Well one thing is the crazy volts they put on the CPU. Pushing the voltage wayyy above max specs no matter if the CPU is -200F will still shorten the life. Also the complexity of setting up to use Ln2 etc. Stuff happens.
Ln2 is used for short benching runs because of the cost. Startup costs are over $500 easy, then you have to buy the Ln2 for runs measured in hours, not days.
Look at it this way. It's equal to the lifespan of a top fuel dragster. Your pushing it way past design limits and uber power. Life is short in the fast lane.