Powers that cost long term endurance

[CLAVDIVS]

What would be an appropriate limitation value for a power that always costs long term endurance when used?

I'm working on a fantasy campaign where many "classes" will have exceptional or quasi-supernatural abilities bought as powers, sort of like "super skills". I want these abilities to be balanced against actual spellcasting (which will use either LTE or a mana characteristic that recovers at a comparable rate, still working on details), so I don't want to tell my players "build the spell as a regular power then divide the cost by X" or something similar. I'd like all the characters' abilities, magical or otherwise, to be built the same way.

[Steve Long]

That's up to the GM -- it depends on how often such things come up in the campaign and so forth. But since costing regular END is a -1/2 or -1/4 Limitation, I doubt most GMs would allow more than -1/4.