Really do not know if there's heating problem, or if this is a problem of this router. My router is on 24 hours a day and did not notice heating problems. I live in Sao Paulo city, Brazil, and in thisweek has ambient temperature of 36C, and had no problems.
I believe some units have a heating problems, not all.
I certainly do not wish to add a fan to this router. Our temps are OK simply using the supermarket wire rack solution.
If ambient temp ever reaches 36C the AC would come on way before that so no worries there.
Is there any study done on temps running at 50, 60, 70, 80, 90, 100% power?
The only fan I tolerate is from the Cisco enterprise router and that is a beast. Easy to pop the hood and blow out any dust from fan and internals once a year