I agree with BobC. One is the risk that they won't let you bring on 3. I travel a fair amount and on various airlines and they all say one carryon and one personal item. So that could inconvenience YOU. And, yes, I get really grumpy when all the overheads are filled and my ONE carryon can't be put there. Just because it gets tolerated, to me doesn't justify inconveniencing one's fellow travelers. And YOU could be in the position of finding all the overheads filled and then have to spend a long flight with all the bags under your seat. Ditto re rethinking.