Psion said:
You know, Crothian, I agree it's not tons of rolls. Nonetheless, personally, I'd rather avoid it. Why is the "wiff factor." Some players get intensely annoyed at their luck with dice rolls, and hinging the ability to even use something on a dice roll sounds like it would really spoil the fun of an entirely too large subset of gamers I know IRL.
In theory, I'm one of those gamers - much of the reason I like playing spellcasters is because it allows me to minimize the role of of the die (the die-role, get it? ...OK, so it wasn't funny). But in practice, I've come to accept that the linear probablility inherent in a d20 roll is simply part of the game, and have come to look for other situations where Crothian's idea fits.
I think the key to elimate the "wiff factor" is in setting the DCs and doing so in the proper way - in this case the "success" point is actually the point at which the ability is spent for the day. Let's use any old 3x per day power as an example: the static DC for failure is 26, and the only "bonuses" are a +5 for every use in the day (for the sake of simplicity)
Use 1: Use power, after use roll the check. Die comes up 8 for a total of 13. The power is still usable.
Use 2: Use power, after use roll the check. Die comes up 14 for a total of 24. The power can be used at least one more time.
Use 3: Use power, after use roll the check. Die comes up 10 for a total of 25. That's 3 down and its still cooking.
Use 4: Use power, after use roll the check. Die comes up 6 for a total of 26, and that's the last use of the power in a day.
Not that in this particular case, a character will still get at least 2 uses of the power even under the worst circumstances, and could possible get up to 5. Further, if the power were instead, say 2 times each day, you could simply adjust the downward by 5 (or upward by five if it were 4 times).
Its a realitivly simple thing, and would only add a handful more rolls each session.