Which totally makes sense. If you get anywhere near a Ward or something, it's probably going to pop your spell. But, that's not to say that your team will always be running into Warded areas every single mission.

Another reason why I look at it the way I do, is b/c I don't always see Mages buffing up a spell with Reagents. Some prefer just to take a lot of Edge, and spend those to ramp up their spells. Which is the same thing IMO... either you're using magic batteries, or you Used the Force, Luke, but either way it wasn't just you.

So if you want it to last for any length of time, you need to account for it with the appropriate Force and the appropriate Drain. One thing that does come up though... is that since you didn't have to declare the Force ahead of time and hope to get that much, you can account for the Force after you already know the outcome.

One Mage wants a big kaboom, so they cast a Force 12 Fireball. But they only roll 1 hit out of their entire pool. So it really doesn't make as big a mess as they hoped, but they're still paying full Drain for it.

Another Mage wants a small kaboom, so they cast a Force 2 Fireball. They roll 10 hits, but they only get to count 2. All the rest are wasted, and they shrug off the Drain.

Or they "call it Force 1", but they spend some amount of Reagents or just spend an Edge. They roll and come up with 10 hits. So the spell goes off with as much as a Force 10. Now they can either maintain it with the usual Sustaining penalty, or they can soak Force 10 Drain and then pass it off to their Force 10 Sustaining Focus.

I'd even be willing to let them scale it back, say if all they had was a Force 6 Focus... using batteries or The Force they were able to get it up to 10 at first, but it cooled down to Force 6 when they handed it off to the Focus. They still had to deal with Force 6 Drain, but now the magical energies are balanced out and can be managed properly.