How long do you think copper gaskets will last on the street as a daily driver?

The deck is 0.025 and a 0.020" copper gasket will put me at the outside limit of desirable quench. If I run a 0.026 steel shim head gasket then I'll have 0.051 quench which is a bit more than what I'm looking for.

Otherwise, I'd have to settle for a 0.029 Impala head gasket which will really put me away from desirable quench.

 

Deck the block and run a Fel Pro.
Copper gaskets leak to much water when cold.

 

I was afraid of that. I was hoping I could get the head closer to ideal quench without having to pull the block and bottom end apart.