The specific example I'm thinking of... none of my players picked up much in the way of resources (only one of 5 players has a +1... just a weird oversight during creation that none of them have fixed)... and while I'm not going to punish them for it, it has from time to time made things more difficult (ie, they found other ways past an obstacle, but the direct route with a bribe or some such would've been easier).
One of them wants to start a session with a declaration/maneuver to say that he's been saving up and has an aspect <Emergency Savings>... something he'd rather not use, but has worked on building up just in case. Resources, difficulty 3 (base for unopposed maneuver) would require him a +2 on his roll... not easy, but possible. Since it's reasonable within the narrative, as well as being possible in the mechanics, I have no problem with it... but does he need to wait until the scene where he needs it to make that roll? It seems kind of odd that if he does it as prep work (which it is, since the saving up occurred during the 3-5 months of down time between games, and can't be refreshed once used), that the bank account would mysteriously cease to exist if not used within in the first few minutes of the game.
In this case, my judgement call would be that he can keep it... but I want to know if I'm opening the door for similar prep-actions breaking the game, or if the book had anything specific to say on it (I couldn't find it, and I figured it may have come up before).