Our APs are built to operate within spec in temperatures up to 50C, so there's no problem in your deployment. As with all electronics, the failure rate will go up as temperature increases, but as illustrated by our lifetime warranty, I would not be concerned about that.
If your power adapter delivers an incompatible voltage, the AP would simply not function, or you could cause a short and permanent failure. If it operates normally, it is unlikely that power consumption is excessive.
Most consumer access points have internal heatsinks (which will get a lot hotter than the back of our APs) in combination with a plastic enclosure with vents. We try to avoid vented enclosures for several reasons, and have been using this architecture for our APs for many years (and millions of units out there).