I got my Flips when they were first released (think it was in January this year?) and the same 9 covers have been in continuous use ever since then, so for the last 9 months. The elastic is still going strong and we rarely have leaks. If we do have a leak, it's usually cos the insert is completely soaked. As sugarpuff said, eventually the wee has to go somewhere and unless you superglue them to baby's legs, if there's wee sloshing around it will leak eventually
I suppose with preloved, you wouldn't know how they'd been cared for so maybe the elastic could go? Say if they'd been regularly soaked or even if the elastic had been very stretched around the legs instead of moving up a rise setting. You'd be able to tell if the elastic had gone by comparing it to one you know is fine. If they are different I would send them back under the 1 year guarantee. If you bought some new you should have an invoice somewhere!
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