the AA's you want to get to extend the duration of buffs is:
Spell Casting Reinforcement = 30% maxed out
and
Spell Casting Reinforcement Mastery = 20%
for a total of 50% extended from AA alone.
you can look in bazaar for a cheap extended duration buff, just be sure to check the LvL of buffs it will help. i can't think of any off hand :-(
another thing you could do, and i don't know how practicle it is for you. is to do the coldain shawl quest. in todays eq these are old old quests, and very easy mobs to kill. the only hard part would be the trade skills required. will need an average of 150ish tradeskills.
if you have this shawl, it adds 20% more for a total of 70% extended buffs, that = 255 min KEI.