Truly not necessary.
Sure they are cute. But what will you do with them once you get home?
They will get tossed into the corner of the closet. Waste of money.
Spend your money on great experiences, not things.
I was in the same situation last year. I've been to the world a number of times and never bought myself Mickey Ears. So on our trip last year, that was the first thing I did. I love them. It's not that much to spend, and everyday I look at them and remember having a great time.
Actually mine came in handy in 2005 in Washington DC at the Regan bldg when 75 Mickey statues came on tour. I wore the ears and posed with the Mickeys and the pictures were great.
My oldest daughter has two pair her first mouse ears in black and then last she she created her own my youngest hates hats so I guess i am out of luck with her.