What are you using these phones for? A pry bar? hahah... I open and close mine dozens of times a day and I realize I'm kinda hard on mine, still no troubles after 2 months.
I would imagine if you contacted your local Sprint authorized repair shop a good tech (not one out to burn you) would be able to order up a new slider covers/track/plates (whatever you want to call them) instead of replacing the whole phone resulting in a replacement fee using your Sprint addon replacement insurance warranty.
I know my local repair rep gutted and replaced everything possible (faceplate, keypad, various internals) on my Blackberry and still couldn't get it working properly then sent out for a reburbished (recieved next day) before I purchased my Epic and never charged me a cent, all covered for free on my $7 a month insurance addon. Take note this was not a friend of mine either, simply walked in first time I've ever been there and he handled everything.
I recommended calling up your local Sprint repair dealer and talk to them.