Hmmm the most reliable scopes really are NF. I have a 2.5-10 that lives in vehicles and never had oil run. Or zero stop issues.
Nightforce is the best scope. By far.
Everything has limits. What are NF published temperature limit ratings? I looked and could not find them. I need to check and see what they are on my Vortex.
http://nightforceoptics.com/pdf/NightforceCatalogUSA_7July_2014_Final_LoRes.pdf