While I wouldn't say there is a kill switch, I might belive that both Sony and Microsoft used Terhmal paste that they knew would wear out just around the time warrenties will expire causeing RROD and YLOD. The thought would be hey we'll know exactly what the problem will be so it'll be an easy fix and w'll spend about $1.00 fixing it while charging the owner 200 to have it replaced.
It's a pretty common game in the industry, I worked for Xerox in the early 90's and they would put these super soft rollers in that wore out after just a few thousand copies. They clearly didn't have to use the super soft ones as the ones deeper inside the machines used harder materials and accomplished the exact same function. The purpose of the soft rollers was to force people to need a service contract which was where the real money was for Xerox at the time. Basically put $0.10 rollers that wear out really fast someplace really easy to repair so the service tech's don't have to spend a lot of time there while forcing people to buy a contract... text book sleazy buisness.