Right now in northern SK I can climate control down to whatever I want easily and about 15 degrees C seems to work well and have been using the Vnish 60-62TH profile on about 20 machines and they have been rock solid.   

I have brains a go and got greedy the first go and landed at about 65 yet temps seemed really reasonable with the low ambient so I let it eat.    Made it about a week and one card went down,  by the end of the next week another was down and limping on the last.
Figured well this is garbage gear I’ll give it another go.   Lowered it to very similar hash rate and draw as my Vnish settings.
Ran rock solid for 2 weeks straight.  I thought ok this might be the ticket.  I wanted to like it!   Then boom.  Sum bitch lost a fan and was merrily tuning away for I’m not just sure how long loading up to 80 degrees then unloading it to a reasonable temp and then back up.
Still haven’t looked at the machine or thought about replicating why it didn’t shut down.
Nonetheless 3 more hash boards down.