Plastic coolant bottle in closed systems

What is the average life expectance of the pressurized closed coolant system plastic bottles with the caps?

I installed a new one about 2 years ago and I think I see a stress crack forming on the front side near the liquid/gas coolant line area. It is still OK but the apearance of that stress crack on the inside has me concerned.

it isn't usually a question of years or miles, but a question of luck. the plastic tank is the weak link in the system. If you see a crack (usually at the casting seam) then it's only a short time until it will crap out. You might consider getting a new tank and carry it and a bottle of coolant with you until that tank craps out. simple swap and go and your back in business...

3-5 years I read somewhere, but can't find it now. Mine is about 4 years now and I don't see any stress cracks, but have an extra bottle just in case I need it. Everyone I have talked with suggests changing over to the later style open cooling system. I'm not convinced yet.

life expectancy is one to two hours.....j/k

I'd say replace it and keep the old one as a spare because this part WILL leave you stranded.I've heard of people having them crack or explode leaving them stuck.

Since we are on this subject again,what is a good trail repair/limp home fix for a fubar tank?

I believe these tanks are made of thermo plastic (probably Polyethylene), so it should be possible to heat seal, weld them in some cases. Unfortunatley the stress crack on mine is inside at the casting seam and not in spot I can reach to weld.

I am not convinced an open cooling system is any better. This is my first closed cooling system, and since I replaced the hoses, bottle, bottle cap, fan clutch and radiator (they were all totally shot) two years ago, it hasn't missed a lick. So far I like it. I am just surprised to see a stress crack so soon on mine.

I don't like the idea of holding the old one as a spare, I even worry about buying an unused one that is already several years old, as I think they have a finite shelf life even in storage. Has to do with diffusion loss of plasticisers over time that makes them more brittle with age, even with out the heat.