i was just curios cause my cousin has jl audio and theyve been running strong for 8 years going on 9 and he bumps them all day and those 12's freaking hit. the only thing that has happend to them is the little cone or voice coile what ever that little bubly thing is, had came off from both the speakers but he just glued them back on and they still sound the same
They will last as long as the material they are made of doesn't deteriorate(i.e. surround rotting away from heat/dust/moisture) and that there isn't any power abuse. So basically, with proper care, they will last forever.