Ability Checks and Caster Level Checks: The normal take 10 and take 20 rules apply for ability checks. Neither rule applies to concentration checks or caster level checks.
Seeing as you really only make caster level checks under some form of duress... that there probably negates it twice over. Potentially wasting a spell seems always like some kind of duress.
Seeing as you really only make caster level checks under some form of duress... that there probably negates it twice over. Potentially wasting a spell seems always like some kind of duress.
If not for the above-quoted rule, the potential of losing a spell would prevent taking 20, but not taking 10, since the point of taking 10 is to take an average result to prevent bad things from happening. One can take 10 on a climb check, for example, even if it's a tough climb and a roll of 9 would result in falling, as long as one is not otherwise stressed or in combat.
I think there was a feat in 3.0 or 3.5 that allowed you to take 10 on caster level checks.
3.5 concentration was actually a skill, no? A con based one if I recall...