my early pencil stuff took forever, but I got my later stuff down to about a week?

Nice progress.

- fullbody sketch 30M
- outlined/flatcolor +3h
- colored/shaded +6h++ (I have serious difficulties in that...)

But the real problem is, that i need exponentially more time if a commission spreads over several days. Motivation and inspiration is nothing that is available every day, especially your day was already filled with work. So i do draw at the weekend usually.

Your analysis really gives good insight of what it is like when you're limited by a day job; it is reasonable to put it in raw number of hours which I suppose are then spread by how much free time you have per day. And indeed it is a problem I have as well, motivation can feel like it begins to spread thin the longer you spend working on it. When you can work hours on end it's easier to zone out and progress in huge leaps.

It is of my concern because I'm looking at how to fit commissions with a 9 to 6 kind of designer job now that I finished college. Depending on how demanding it turns out to be I'll have to accept less orders than before, and change the turnover rate expectation on my ToS.

yeah that's the point! Besides you are doing great with your turnover rates! But one thing I recommend: If you see spare time is getting rare, then do not accept time intense commissions. I did this several times, because of a thrilling theme, but it ended in a mess. As I mentioned: working time grows exponentially, if you have to spread a commission over several days, also the quality of my work was free falling... At the end i was working on 1 piece over months without any updates, while my followers were thinking I was dead.

Just do small stuff you can get done in your spare time without compromises instead of driving yourself into burnout. Keep yourself in practice and wait for a good time to do something great ;)