Yeah, it's complex because a number of physical phenomena occur simultaneously - it's tough not to just pick one attribute and say, "see! this is the answer!" without all the others.
Durability is affected by the loads (torque) and viscosity of the oil. As load goes up, temperature goes up, as must the viscosity of the oil to keep the moving parts separated. That's why the extreme loads of a top fuel drag engine requires extreme viscosity grade engine oil.
Yes, the higher oil viscosity adds viscous drag to the moving parts, but they would wear out quickly otherwise, negating the use of thinner oil!
It is also true that lower viscosity oil absorbs more heat - but the oil doesn't do the bulk of heat rejection - for an average engine, 1/2 of the heat goes out the exhaust, 1/3 out the coolant, and the remainder radiated, if memory serves. Something like that, without googling (used to have this memorized 20 years ago).
Yes, engine temp is limited by oil longevity, really. I published the exponential oxidation rate of oil with increasing temperature some time back. Not gonna re-look it up again. Something like 220-230 degrees F is optimal for a synthetic oil for 5,000 miles OCI's like we need to do to keep engine hydraulic orifices clean.
I don't understand why anyone would run a 180 degree stat. You shouldn't be running oil that long in this drama queen motor in the 1st place, and it lowers your fuel efficiency too.