Not too sure to be honest mate, but it is a good idea. I had it done on my S2 and it's in the S1..like you say: just for piece of mind.

sufsRS, I think he means on a switch. If it was on perm, then it would take ages for the car to warm up, and there would be no need for the fan to run when the car is travelling, so a waste of time. I don't think that it would increase the tiring out of the fan by a great deal neither (unless it was perm on) as all it is doing is switching it on slightly earlier than it *may* already cut in at. More of a safe guard so that you can decide when you want the fan on. As said by Dry, the therms can become unreliable with age, so why risk it. I think it's a good, easy, cheap & worthwhile mod.