Why back cover falls off.

Fitbit Charge HR seams to have a very common problem of coming apart in the back along with the side button falling who knows where! This makes a good product in operable if owner has had it past a year (or what ever the warranty date is)!! There's no way to get it fixed & Fitbit offers NO parts to customers (who have paid well over $100) a way to order for self repair!! Is this a set up for customers to keep purchasing their products, yearly or so?! Are the Fitbits made to last only a short while and we aren't being told?! The new Fitbit is very attractive & seem to be a step up from the first run /previous generation, however whose to say if they will hold up past a year?!?!