I find that I can average 6-7 hours of sleep during the week, but I need to catch up on it A LOT on the weekends... typically get 9 hours on Fri and Sat nights, and even include naps on Sat and Sun here and there. This past Saturday, I slept an incredible 13 hours! But I'm also very active - I typically exercise at least 45mins a day 6 days a week.
Nothing endures but change.
Only thing I can recommend is more exercise and maybe looking into your diet in order to get more energy. You shouldn't need more than 8 hours a night, but then again, if you're in a constant manic/hypo-manic/manic-like state (I'm not sure of your mental health diagnosis) then I know you can need more.
Also, just curious why you avoid caffeine? It might help in this case, but I don't know other details about you....
The only other thing I can say is, at least you know what you need to function well - if you can't tweak anything else, I suppose you should just make it a priority to get 10 hours of sleep a night. Think of it as a healthy thing to do rather than something that's wrong with you.