Well, if you take the books as an example, I believe there were a number of occasions where large groups of victims were bled. How many Fate points do you want to hand out when that happens? Alternatively, a caster could simply give himself a minor consequence roughly every hour. Which means that even if he kept to business hours when doing so, he'd be getting 40 free Fate per week (over 100 per week if he 'worked' overtime and weekends). Of course, when I say 'work' he would, of course, have about 55 minutes of every hour free to do whatever else he felt worth doing.
Oh, and if he had Endurance 5, then the numbers double, since he'd have two minor consequences to play with. And if he happened to have a Recovery power, then it becomes even worse. Even with very conservative rulings limiting each 'scene' to an hour, a character with Endurance 5 and Inhuman Recovery could heal back the two minors plus the 'instant' minor, plus a moderate every hour, for 5 Fate per hour and around 500 or so per week. More, actually, since he can get away with sleeping only every other night. Call it 700 per week.
How long would it take to store up enough to explode the planet? How many zones does a planet have, anyway? Ok, let's think smaller. How about wasting a city?