The answer is a clear "it depends on...".
Living in germany (with normally not so hot summers, you know what I mean
), I keep mine in a small rack. In my room I've normally a temperature of 25/26°C. So I use a heat cabel conteolled by a thermostate, which gives them 28°C on the warm side - dropping to 25°C on the cooler side.
With higher room temperatures it might be unnecessary to install heating. And to be honest: I've made no bad experiences with slightly lower temperatures at around 24/25°C but really bad ones with too high temperatures over 30°C...
Best wishes,
Seriva