At our club we use 21mm Yellow minipins for on road
indoor racing ( wooden floor )
Really, if you want good grip then you need a full set of tyres every week ( 3 races and one practice )
I agree, they dont seem to last as long as they used to. I suspect its partly to do with the advent of brushless/lipo. They are sure to wear down at a quicker rate due to the increase in power and the way that its delivered.