Even if the warranty remains intact, don't buy it. I don't think it's worth it. I don't have any links on hand but just google for it. There have been various reports about the cooler melting onto the 360, burning the case, etc.
Also, there are articles that discuss how the cooler mishandles power. Here you go actually - http://www.xboxic.com/news/1879
You'd be better off buying a small desktop fan and angling it perpendicular to the 360's exhaust. Also, try lifting the 360. I have all my consoles on a grey milk crate. It provides airflow all around my consoles.
If you don't want to do that, you can cut out a few equal sized pieces of cardboard, square or circle, hotglue them together and place them under the rubber feet of your 360.
Personally, I have a hard time believing the 360, by itself, causes your room to become 90-95 F. But hey, you never know.