It does depend on the type of hulls.
The foam/kevlar boats keep going really well - the only problem being that the earliest foam/kevlar boats (up to 18yo now) were built with finer hulls that are not as buoyant and do not manoevre as well as the more recent designs (90s).

My foam/kevlar Fay hulls are approaching 10 years old and are as stiff and competitive as new ones except that they are now around 2kg over weight. The day I make so few mistakes on the course that 2kg would make a difference I'll trade it in for some new Boyer hulls.

As for timber hulls. I have no experience there so I couldn't tell you. I would guess it depends a lot more on how well the hulls have been looked after.