Personally, I say go for AA when you want. It may be more efficient to wait till 65 but with 1-50 going faster (AAs) than normal XP - I say go for AA when you like.
Personally, I will go for a mix of AA and Normal Levels as I desire - once I get to the appropriate levels.
I started at 65 for all three of my characters. I find melees can probably start them earlier and not worry too much, whereas casters need their spells.
However, I'm the sort who can't wait to hit level 65, it had nothing to do with my AAs.
Yeah, it seems silly to me to do them before 65. But hey, I saw a venerable who was 64. Weird? Kind of. Stupid? I dunno. I'd prefer to get 65, finish off leveling, and then make the switch.