I know there are some spells that have had their duration altered. I would like to suggest a few more since PnP doesn't quite translate over into NWN (fights are over MUCH faster and there are a LOT more of them).
Below are a few suggestions for changing spell duration from rounds to turns. I do not want to overpower or break anything yet some of these would certainly make spells more viable and less junky.
Expeditious Retreat
Druth's Necrotic Shield
Elemental Shield
Displacement
I changed Displacement a few updates ago, so there's more of a reason to use it.
The others I'll certainly consider, though I'm a bit leery of extending duration on damage shields.
They can already be extended for very long times at appropriate levels.
They're all rounds/level (i.e. 6 seconds/level). A level 30 caster extending the above spells will have them for 360 seconds, 6 Minutes. Define very long.
Long enough to be effective for most entire spawns or boss encounters where you would need or want them.
I often use Expeditious Retreat against bosses

I'd agree possibly if there weren't almost matching spells with much longer durations.
What do you see as matching Elemental Shield with a longer duration? Mestil's Acid Sheath is also rounds/level, no? And Death Armor is very weak.
I was looking at it from the perspective of immunity but I think you guys are right, that duration is fitting for elemental shield.