If you are in it for the long haul you can also do alteration till you get your epic (our is a major pain in the ass to get), then respecialize in Solro to conjuration once you have it.
My reasoning is: while leveling up buffs do get cast most often but once your 60 you're mostly going to be doing raids or random quests. By then you have group magic resist and your other buff spells have a good duration. Haste and C are the only buffs you will be spamming and the epic takes care of the haste.
So basically I'm completely contradicting what I posted a while back as another option.
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(P.S. This is taking into account that this server stops at Velious. If it didn't then I would stick with alteration all the way due to the AA's and the haste you would be getting with PoP.)