once upon a time i liked having extend on my pale master because it basically gave me a visual reminder to renew my elemental spell damage clickies.
however, those clickies have now been repeatedly and brutally kicked in the unmentionables with steeltoed boots. wrapped in sandpaper, and encrusted with salt.
as a result, i no longer really care whether my auras are extended or not (well, that and the bonus caster levels would have really thrown that off anyways).
extended buffs... well, if spending an extra 10 SP to get 50 minutes worth of blur is actually saving you SP as opposed to costing you SP as a result of hitting the shrine well before you would need to refresh it, you're really, really, really taking your time. actually, if you're going 50 minutes before either completing the quest or reaching a new shrine, i'd be surprised if anyone's actually surviving for that full 50 minutes.
but seriously, i'll take +1 DC to a single school that i'll use frequently any day over the chance of the extremely unlikely corner case of "oh man, if only i had 25 more SP, i'd totally destroy this quest" happening. seriously, if the tiny benefit was that valuable, you'd see people taking mental power for reasons that don't include "i want it to qualify for something else that is actually useful, like wraith form or archmage PrE" or "i didn't know any better when i chose that feat".
(on a side note: insightful reflexes is useful in far more than 1 or 2 quests. having a good reflex save is amazing in almost any quest you care to name, whether you have evasion or not).
Consider that 3 Spell Pen on a non-Elf costs 12 AP, while 3 Spell Pen on an Elf costs 5. Or you could trade the DI Spell Pen twist for 6 AP. It's less about having a higher max (although that option is open to you) and more about having a more cost-versatile same.