ok i did a itr spring/shock/ rear Lca swap. everyting but the shocks were new. the seller claimed to have about 10000 miles on it. they good when i got them but now im not so sure. i have them on for about 8000 miles or so. Has anyone had problems with there shocks wearing out prematurely? my fronts feel fine but the backs feel way looser? what are the symptoms of blown shocks anyway?

thanks in advance