I used to think thermal paste was a 'one and done' thing for years

I was working on a gaming rig in Austin that kept overheating after two years. I opened it up and the paste was dry and cracked, like old clay. The owner said he never had it serviced, and that was my light bulb moment. I always told people paste lasted the life of the build, but I was totally wrong. How often do you guys actually re-paste systems for clients?