I have two pairs that I got in an outrageous end-of-season sale a couple of years ago. I mainly wear them for kayaking and wading, so my feet rarely get too too hot in them, and I leave them under the house with my 'yakking gear so even if they did smell bad, I don't suppose I'd notice much.

On the other hand, I did have a pair of Tevas that got awfully smelly after just a few weeks of wear.