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Like the rest of you, I am not concerned about the firearm's heat tolerance, and if it is properly lubricated, it should stay that way. However, constantly subjecting the ammunition to temperature extremes, over a long period of time, might not be the best for it. And smokeless powder's burn characteristics can vary with temperature, though these differences are insignificant when considering handguns used at close range.

Plastic shotshells may not fare very well in overheated motor vehicle compartments, but that is admittedly a little outside the scope of discussion here.

For those who still wish to be cautious, a well-fitting windshield shade and cracked-open, tinted windows and moonroofs might help mitigate temperature extremes in parked motor vehicles.

Brownells and Midway are two good sources for firearm lubrication products.

I'm at the range at least once a month, so the gun is cleaned/lubed at least that often. I don't keep my carry ammunition for more than 6 months. I'll fire it off at the range and replace it. Just one of those habits I got into. Didn't want old ammo to fail on me when it matters. ;-]