I have to say that my experience with FitBit support is the opposite - even when I couldn't produce a proper receipt, they sent me a free of charge replacement when it turned out my original Flex was a bit of a lemon, battery-wise, and they twice replaced my charge when the band broke*, with the second replacement actually being done outside of the warranty period.
Where I'm peeved with them is over their support (or otherwise) for current mobile devices - as long as you go for an Apple device, you're fine, even up to the latest model of iPad and iPhone. Android, not so much. My smart watch really shouldn't get a say in which phone I upgrade to!**
*Partially a design flaw in the charge - you can't replace the band like you can on the flex - and partially an issue with their sizing; I sit very uncomfortably on the cusp between their two sizes a large is way too large but a small is not quite big enough to stand up to my wearing it 24/7 (nb I've had the exact same issue with most watch straps over the last 25 years, so all I can assume is I have weirdly sized wrists!)
**It wasn't a huge say but it is what tipped the balance - granted, I've probably ended up with a better phone, but still *grumble*