I am sending a hug your way today! You know I always wonder what is helpful to share on the board, what is helpful to put in the guide, and what is helpful to put in the catalog. You'd be surprised to know HOW MUCH we talk about this, as everything cannot and should not be shared everywhere. 
Carrie and I began jotting down approximate times for each box first to figure out about how long we thought each child's homeschooling day should be, considering their age, maturity level, state standards, etc., and keeping in mind how busy all of us homeschool moms tend to be. 
Then, as we did the guides with our own dc , we made schedules/routines to try to get some order in our days. After finishing a guide, the next time we did the guide with our next dc, we found we were pulling out those old notes again to try to better plan for our days. As we found the approximate times so helpful, we thought others may find it helpful as well - hence, the putting them on the board. Because finishing each box in the suggested time allotment is not a "have to", we decided not to put the time allotment suggestions in the Introduction of each guide. The alloted times are meant to be a helpful tool for planning your day, but should you have a child that takes longer than the suggested time allotments that is working well and doing excellent work, I would call that a pretty successful school day!
I think it would be far worse to have a child finishing in the alloted times and doing poor, incomplete work. So, there are many ways to have 'success' in homeschooling, and in the scope of things, it sounds like your ds is very successful in his school. However, if you are feeling frustrated about him taking longer to do his work, you have already received some good advice. I think that dc who are creative take longer to do projects. We found this to be true with our ds, Riley. Here is an excerpt from a past thread where I shared about this...
...Well, keep in mind that I'm referring to my sweet Riley, who is very creative and would be quite fine if school took from sunup to sundown to complete. For his writing skills, it took him about a month to become skilled at doing 1 vocabulary card. This involved many new wonderful skills - using contextual clues, using a dictionary, copying definitions, applying all of that knowledge to using that word in a sentence of his own, and finally filing the card alphabetically in a card file.
Learning to write well on lined notebook paper for R & S English took him a few weeks to figure out. I limited his writing to 3 things. The rest we did orally or on marker board. For DITHOR, I first wrote his dictated answers for him in his DITHOR Student Book. I did this for about a month. I then wrote half for him in his Student Book, and wrote the other half on a markerboard which he was responsible for copying into his Student Book. We did this for another month. Around the 3rd or 4th month of DITHOR, I believe, he was doing all of the writing, and I sat near him to jot any words he needed help spelling on a markerboard for him.
It took him awhile to write his science lab sheets well. I first set up his paper for him with the "Question", "Guess", "Procedure", "Conclusion" words written on the paper for him. I put a sticky note under the "question" in the BHFHG manual, so he could easily copy it. I helped him with his guess, and I was not hard on him about this. Any guess he'd tried to think through I accepted, even if it was totally off. We did the experiment together, and then I asked him how he could draw it for the "procedure" part. I drew a rough sketch of what he wanted to draw on a markerboard, so he could see how this could look. I asked him the question again, and I wrote this on the bottom of the markerboard, so he could copy it for the "conclusion". I often referred to the "Key Idea" to help him come up with the conclusion. After about 4 times of this, I just helped him set up his sheet, put the sticky note under the question, oversaw the experiment, and let him finish out the rest of it on his own, helping only if he needed help with spelling or a key idea conclusion.
For the notebooking, the biggest things he needed to learn were to follow step-by-step directions from the BHFHG manual and to use the entire space of the paper in a balanced way. I believe the first notebooking he did he tried to draw a very tiny something in the center and had very large writing all over the top. We talked about making the picture fill the center of the paper, using a ruler to help with the heading, writing in medium sized letters, etc. I worked the whole year to help him learn to follow step-by-step directions for notebooking. I taught him to first read the whole box through and visualize what the notebooking paper would look like. Then, I taught him to do one step carefully at a time, and last, to read through the whole box one more time at the end to make sure he'd done it all. I was always ready to help with any part of this, but more and more as the year went on, he was able to do this on his own. We started just doing a "talk-through" of the assignments. Where he'd read the box to himself, and then tell me briefly what he was going to do (i.e. pointing to paper he'd say "I write the title here, draw "X" here and color it, label "x", and write this quote at the bottom here"). This was a quick way for me to see that he understood what he would be doing without me watching his every step while he did it. We did this kind of "talk through" for art too.
Time management skills - well mainly this was just learning to be aware of time passing and that he should be wrapping things up by "x" amount of time. Mainly, it was artistic projects that he tended to take quite long to do - he'd forever be choosing which shade of pencil or crayon to use, which yarn color he liked best, whether to use glitter glue or glitter and glue, you get the idea. I finally decided to just give him more time on these types of assignments, as he loves being creative, and I didn't want to rush him. Setting the timer and giving him 10 minutes more than I used to give Wyatt helped immensely...
Here is another past thread where I shared why we went half-speed for quite awhile in BHFHG...
With Riley I went half-speed with Bigger Hearts last year for around 12 weeks or so, so we started this school year on about Unit 7. I thought for sure he'd be ready for full-speed. We tried it. It was still too much. He could do it all, but it was too hard to get him to do it. He actually loves to take his time with creative, art type projects, and this made the day full-speed too long for him and too frustrating for me as I was herding him along. So, back to half- speed. About Unit 15 or so I believe, he was asking for science every day, and reading history every day, and he wanted to do dictation every day and math too, and as I was contemplating adding some things to his day because he was finishing his half-speed so early, I realized perhaps we should give full-speed a try again. We did, and it was a good fit. So, I guess I would say to watch for signs such as that, and then give full-speed a try to see how it goes. I think you will know then. HTH!
So, going half-speed for awhile, planning some extra time than the alloted times for ds to work on more creative things, and moving the 'extra time creative' type things to be finished out at leisure at the end of the day (so ds can take his sweet time, but you can be done with your teaching portion and get on to all of those other manager of the home type things we homeschool moms have to do
) are my best tips. I hope something here helps, but I think you can really feel so good about ds's great work in school, and focus less on the time allotments! You are doing a super job with ds, so keep up the good work and celebrate the journey!!! In Christ,
Julie
