Thank you for your most intrecate answer!
In my system (as it stands) stamina is (sort of) represented by action points and mana by, well mana. I do like the idea of actionpoints being able to be burnt to regain mana but then slowly to increase the value of mana.
I have spells that can burn...
So here I am creating my own roleplay system. (Yes I know there already are to many unfinished once out there) (It is well under way btw.) So. Mana regen. Due to the inherent lack of a computer and the clumsiness of the sleep-to-regen-mana/spells I have saved this topic for some while in order...