No.
Running your fan at 100% makes your Xbox a noisy beast that will frustrate you when playing quiet games or watching movies.
Some very well-informed Xbox software developers accept temperature ranges in the 60C+range as acceptable, as the basic Pentium III chip has NO problem dealing with these temps over extended periods with no failures. It is a tough old chip.
Cooling is a contentious issue. I live in a bloody hot and humid climate and have adjusted my fan speed to 40% to compensate for the long hours that my Xbox is in use as my DVD player and media center. I also made other alterations that were probably unneccesary for the Xbox such as cutting the HD tray. The fresh thermal grease is a cheap and easy mod, and good for older boxes.
But - don't obssess about heat. Xboxes are robust machines designed for tough use.
Quiet operation beats a couple of degrees lower temps IMHO.
Best test - use XBMC, set your max temp in "system" to whatever you are comfortable with and see what speed your fan runs at.