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With probably 700mm of tube between the primary and secondary mirrors a quick bit of googling suggests that 1 degree of temperature change of an alloy tube will shift your focal plane by a couple of hundred microns, assuming that you are using the ASI294 camera your critical focus zone at F4 is about 40 microns. Given that, it is certainly worth refocusing a couple of times during the night at least.
On my SCT in hotter weather (Using an automated focus motor) I was refocusing after every second 5 minute sub, better to throw away the time I could have used to get half a dozen subs in the night than to end up with heaps of soft subs. That certainly happened a few times before I automated focus.
I have a Celestron focus motor on my SCT and the ZWO one on my ED72, I am a bit tempted to sell the Celestron one and get another ZWO unit to fit to it if I keep imaging with that scope as the Celestron focus motor lacks a temperature sensor, hence refocusing every couple of subs.
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