I don't think anything "happens" to your keys if used to upgrade, period. The Digital Entitlement is for the hardware. I don't think the key used to upgrade is even recorded with that info. I can't prove or disprove that, its just my gut feeling based on all the info I've seen. People have installed the same Windows 8 Retail on multiple PC's (one at a time with the same key) and then did the free upgrade. If the key was recorded that should fail on the second PC you tried to upgrade from that same Windows 8 retail key. They say it didn't?