Copper water seals?

[classicauto]

If the plates and water seal grooves are in good shape, the car doesn't get overheated (ie. the rest of the cooling system is sorted for the use of the car) and you don't put washer fluid in your radiator the OEM's should last a very very long time.

I'm not aware of any actual copper ones, just the mentioned "heavy duty" versions. Personally, if you're toasting OEM coolant seals regularly, you'll likely have problesm with heavy duty ones because they are a symptom of another problem - not the cause.