Nominal Lifespan of Boats

While I know in reality the lifespan of a boat depends on any number of factors(how often/conditions you paddle, geographical location/uv exposure, how it's stored, bad luck knocks or surf can certainly break even a new boat, etc.) what is considered the nominal/typical expected lifespan of gel-coated(excluding the spec skis or exposed carbon boats like the Epic GT where the exposure to uv and stiffness when it comes to knocks might skew the average) boats in normal(excluding rocky down river races/huge surf break) use?

And lifespan defined as before any repairs, as I imagine in the hands of a skilled repair specialist you could extend the life considerably if not indefinitely(I imagine there would be a point where the cost/benefit of repair would exceed that of buying a new boat).

All other things being equal any difference for glass, kevlar, or carbon?

The last ski I bought (Carbonology Flash) I opted for the hybrid construction for a good mix of robustness and stiffness (glass with carbon section through the centre), only 1 kg heavier than full carbon but also around $1,000 cheaper.

The result is a boat now in it's 6th year that has been paddled on average 3 times a week. Lots of riding breaking waves and ocean paddling.

I have had the rudder area repaired a few times from knocks and its had a general tidy up of scratches to the gel coat but it has never leaked and is still going strong.

It has been stored undercover but outdoors and not in a bag or sock.

I still think the hybrid layups are the best bang for buck if you intend on holding onto the ski for years.

Not exactly a ski, but I have a kevlar skin coat (no gelocat) north american open canoe from 1987 thats good as new, I had a different one from 1983 that was just slightly brittle, but still very serviceable.

I also had a V10 from 06' for a little while that wasnt showing any signs of dying.

Resin is good for a long time. The main determining factor is probably abuse (rocks, drops, surf, garage roofs, gale force winds while driving, excessively tight straps, ect). I'd say human inflicted damage is what ends a boats life much more so than anything else.

Based on my experience with yachts i would venture that fibreglass and the epoxy resin skis should last up to 50 years if cared for. The sandwich contruction may start to delaminate a lot earlier though particularly if exposed to dramatic temperature changes.