I've had all 3 gens of FitBit and never had hardware issues. My gripes have all been on software (refusing to integrate with Apple Health, I don't like the new "sleep score", and I don't want a "premium" monthly payment). I did upgrade when the previous ones were no longer functional, but I had used them constantly for a few years each time.
However, I used to leave the charger plugged in my bathroom because I would charge it when I showered. I noticed the charging posts got crud on them and got smaller over time until my FitBit would no longer charge. Eventually, I started unplugging it except for when I was charging and that fixed my issue.
However, I used to leave the charger plugged in my bathroom because I would charge it when I showered. I noticed the charging posts got crud on them and got smaller over time until my FitBit would no longer charge. Eventually, I started unplugging it except for when I was charging and that fixed my issue.