Hi,
I live in Nth Queensland Australia, where in summer it is nothing to see 36-38 degrees C with 80-90% humidity and everything in that temp under load starts to suffer. All the leading Arborist compaines (and I have asked ) up here regardless if they are using Stihl or Husqvarna run their saws anywhere from 25-30:1.
Now these guys use there saws all day and use them hard, they are not bothered if the saw smokes a bit or smells funny because of the burning oil. They are only interested in one thing, saw longevity.
Now I am not saying you should run your chainsaw at that, but if you are only using it for a weekend saw, for fire wood or a collector I think 35-40:1 is more than safe. I have friends and other collectors up this way who run their saws at 40:1 and that is exactly what I run my saws at. I have new saws and old vintage saws and they all get the same 40:1.
It is totally upto you. As long as your are using good quality oil and not using the saw day in day out commercially, anywhere from 35-45:1 is a good safe ratio.
Cheers
Justin