Every component has a MTBF directly affected by heat. Every reflow cycle has a small chance at popcorning/delaminating something no matter how careful you are, and you may not hear it even if you're listening for it. And we may not know when a GPU is on the way out and we killed it by swapping, so it could just need another new GPU.
I know a lot of things we talk about here are specifically about getting your own unit working no matter what so the waters are muddied by arguing from two different standpoints, but from the perspective of both turning a profit AND providing a warranty, you stop after a few cycles.
edit: and to
@RIP-Felix's point, I still think the TOKIN crowd is a little nuts. But that all started like 2 years ago, and I give a 2 year warranty on Franks, so that's 4 extra years since I went apeshit on everyone while it does seem to be getting worse. Plus I am literally finding it easier to replace them than to answer a hundred questions about why I didn't replace them, so I just rip them off these days (the thing I was trying to avoid by trying to stamp out the misinformation early) on the more expensive configurations. Seems like it helps justify the cost to customers as well.
edit 2: Also, in my experience, heat KILLS the TOKIN caps, so if you've reworked a board like whoa, you really should rip them off at this point.