What Paul is really saying is HEATSOAK. Feel the smic after a good drive, esp in traffic, then you will know. Because i know.
They MAYBE good fo upto xxxkw, but how will it cope with the heatsoak? Unless you have a waterspray AND a decent fan on the smic - its pointless. And by the time you have bought an upgraded smic, waterspray kit, fan, ducting, you would have spent TWICE as much as a decent fmic kit would cost, and you would have spent twice as much time as well, and you still wouldnt be happy.
There i said it!