Well... my husband is 2 yrs older than I am..... so I suppose that doesn't help
I've always gotten along better with people older than me in all relationships... not sure why, that's just how it's worked out.
As far as an appropriate age for a 10+ yr difference... I don't know that age really matters if the relationship works and the people involved are happy. I suppose if one was 25 and the other was 15... might be an issue legally, but I just figure if they're happy and it works well.. there age really shouldn't be an issue.