I guess I'm just lucky. I've got a few piles of stuff I've replaced because of upgrade-itis, but only one pair of full finger gloves don't work. As a result of that and Pearl Izumi's shrinking sizes, I buy gloves in person now. What doesn't work for me in the 30s works in the 40s, and so forth.
I might add that some event-specific jerseys are not made to American sizes, and I've got a fair number of "2XL" that won't fit me even now that I'm down to a size L. Grr.