to many variables in that question my friend. it depends on many different things all the way back to how the resin was mixed in the first place. quality can very widely ( or wildely :rolleyes ) depending on the manufacturer. also can depend on how a boat spends its days . . . abused race boat or trailer queen . . . .ultra violet rays play hell on fiberglass quite a bit too. if you are looking at a project best bet is to get a pro to look at it, someone that knows structural fiberglass.