4th, this is what I do all the time, and very important. If you play more then 1 hour of gaming, always go to the dashboard and let it sit for 5 min, this cools down the 360 as its not tkaing a load or using more heat, then it cools down. Theres a cool video showing this should u wish it, let me know and Ill post the link.
Good luck.
You're not helping the console any by doing that. It doesn't matter if you play for 5 minutes or 5 hours. The 360 hits it's operating temp very quickly. Once it hits it's peak (during gameplay) it'll stay around that range for the duration the game is being played. So it doesn't matter how long the console is being played. It's not the temperature which kills the console. The console operates just fine at it's those temps. It's the repetative heating/cooling/heating/cooling going from room temp to full operating temp.
That great temp variation stresses, weakens, and ultimately destroies the solder. The easiest solution would be to turn on the 360 and never shut it off again. That way the only temp variation would be from idle up to gameplay, which wouldn't be a lot. But of course, we all know that isn't practicle. So the only option is to lessen the difference in temp variation, which is being done with smaller dies, added fans, better heatsinks, etc.
Long story short... don't keep stopping gameplay to let the console cool. It doesn't help and you're just cutting in to your zombie-crackin' time :)