Raising the PS3 as suggested above would do nothing. It has no vents underneath it. The rear is the important part as this is where all the airflow happens.
The yellow light of death is your worry, and this happens when the crappy lead-free solder used on the GPU gets too hot, connections break, and then you get a yellow light. For most people this happens when they play for a while, then shut off the system and the next time they try to turn it on, it has a yellow light because the solder got too hot and stayed too hot for a prolonged period.
What I suggest for customers after I fix the yellow light is this. When your done play, return to the XMB dashboard and let the PS3 sit there for 10 mins. This will allow the excess heat inside to vent out, but the system isn't under load from the game anymore, so it isn't generating anymore heat, and this also allows the solder to cool back down at a steady rate and not just play for 5 hours, then shut it off, with the solder extremely hot and no air venting out.
I have fixed over 1000 PS3's from the yellow light, and heat and the GPU solder is 99% of the issue. If you can try and get the PS3 rear near the back of the rack near an opening and do as I suggested, you might be ok. It's still a crap shoot.
If you're extremely adventurous, you could open the system, clean the fan blades off and replace the thermal paste with something like Artic Ceramique. I would do that, but that's me. After taking apart them for years, I can do it easily. There are lots of guides online though.