I've never used fans on my AVRs. I forget if it was my Anthem MRX500 or the NAD (model forgotten) which got so hot you could cook your breakfast on it. Didn't seem to do them any harm.
I ran my A8A quite hard a couple of nights ago, playing pretty loud music. Checked the temps with an infrared thermometer. The top of the unit at the front never went above 32C, though at the back it reached around 42C. I'd have expected it to be the other way round - as the actual amps are at the front - either side of the transformer.
Out of curiosity, just measured my A2080 and that's at similar temperature despite light load at the moment.
Both are in open-backed cabinets with an inch and a half at each side and a couple of inches above. The rear of each extends a couple of inches beyond the back into free air.