Duration of a spell or commune is generally based on level. For spells, the veil can also impact spell durations. Spellcraft will improve the level you cast at and therefore also help durations. For druids, your herbs can impact your prayer durations. Edges can improve duration of certain affects as well. There are probably other things that can also effect duration in some fringe cases but those are the big ones off the top of my head.

The percentage you have learned the spell or commune only effects whether or not you fail at it (lose concentration), edges you can learn if they pertain to it, or open up new skill avenues (ie, assassin kicks).

This was explained quite some time ago, might want to try digging through the search but the players who spoke with you are correct.