I run all my V56 cards in my shed, they are set to run at 60C, but i have several exhaust/inlet fans in the mix to keep it there. using about 6kw @ 150/ea do the math.
In general, the cooler you run them, the longer they'll last. Especially the capacitors.
Also, for all those trying to run multiple carts..
Custom Resolution Utility is your friend.. a little utility called restart64.exe
Run this on a script on startup, it re-enables HBCC for all cards in the system with no fuss.
You heard it here first.