I have no problems with that. My experience as a retailer is that it's pretty much always the same customers who return things over and over again. Of course I never complain about people who return items still in new condition so that they're easy to resell. It's the ones who are trying to exploit a warranty over and over again, or returning items for frivolous reasons after putting noticeable wear on them that I take note of. Those are the customers who are costing the business money in the long run. Honestly, if I lose one of those customers because I refuse to accept an item they're returning for the third or fourth time I won't be all that sad about it.
People like to do that with waterproof boots. I pretty much know the customers who are going to buy something with a 6 month waterproof warranty, wear it 5 1/2 months and then bring it back for a new pair because they claim they're leaking. I'll usually give them that first pair, but if I see them coming back 5 1/2 months later AGAIN, I know what's going on there. Still I'll usually make that second pair good as well, but there will be no next pair for that customer. The price of shipping their "defective" items back to the manufacturer for credit will have already eaten up basically all the profit of the original sale at that point anyway, and I've essentially kept them in new boots for a year and a half.
I would chalk it up to a genuine defect if it wasn't always the same people who tried it. I've come to the conclusion that some people are just self-entitled scum.