depends on what coilovers. and quality.
a friend of mine had dms gold 50mm's in his wrx, used them for two autocrosses, and maybe 6,000 miles, and blew a damper. those are near 3000$.
other people have 800$ megans, beat the shit out of them and never have problems.
and ALL coilovers wear out, and need to be rebuilt. and maintained.