Not having devoured the rulebook yet (waiting for my hardcopy), I'd throw this into the mix:
Since the spellburn mechanic is part of playing the game, used to improve critical rolls -- and make the game more exciting, first and foremost -- a wizard can decide...
1) Make this roll at the end of an adventure. If you burned during the adventure, that still applies to this new burn, i.e., you aren't starting from 'full' (unless you were frugal during the adventure, saving up for this new roll).
b) Make this roll at the start of an adventure. Whatever you burn now, is already burned for the course of what is to come...
Even if, logically speaking, the 'downtime' between adventures would allow a full healing, the game is played 'at the table' so to speak. Spellburn has consequences, we're going to represent those consequences in this way. We're playing for maximum fun and drama. Gambling has drama; rules-lawyering and weaseling out of side-effects has no drama, no fun, and no soup for you. Want to make a character that does everything important behind the scenes and only with no risk of danger? Fine. But that's not what we're playing here.
Option b makes a fair representation of an example from above: Yes, you did your burn in downtime, but the icky, creeping flu you caught in the process is still with you now. Roll for initiative...
Gnome Boy (a.k.a. "Jon") • DCC play-tester @ DDC 35, Feb 2011. • Beta DL 2111, 7:00 AM PT, 8 June 11.Playing RPGs since 1977
• Quasi-occasional member of the Legion of 8th-Level Fighters.
Link: Here Be DCC Monsters