is hooking up your macbook pro to an external display worth destroying its longevity?

I'm starting to wonder if whether or not plugging my macbook pro into an external HD monitor, worth destroying its longevity. As you all know, when you plug in a macbook pro into an external display, your laptop gets insanely hot, and is running on all cylinders. Given that I do not want to destroy this $2000 machine that is over 2 years old now, is it best to simply invest in an iMac? Is it a must? Has anyone here plugged their macbook pro into an external display regularly for a long period of time? 1 year, 2 years? 3 years+? How is it holding up?

I know my macbook pro is built like a tank, but there's simply no way it's designed to be running at over 100F for 4hrs+ per day.

What do you guys think?