I only know what I've read from other users. Hence my comment as to many of the 10-year warranty purchasers selling their cards to upgrade after a few years, which seems to be the most common outcome I googled.
Any card they send back has to be equal or better performance, and EVGA will err on the side of performance. So that limits what they can send back if you send in flagship model cards.
Regarding the 8400 and other ancient hardware... surprising they are selling that stuff. Be aware not all of it meets the required -KR model. I wonder if it is a holdover from when EVGA was selling everything with lifetime warranties and they simply kept a lot of extra stock.
The only card I've personally warrantied from EVGA was a GTX 260 that was maybe a year old (I forgot why, errors or coil whine), and got a GTX 265 model back. My Titan Black was an OEM model with a puny 1-year warranty which had passed, but EVGA to their credit did attempt to fix it when I sent it in for repair. They repaired the VRM to get it to power up, but didn't charge me when the repair was deemed too costly to complete due to a partially fried memory chipset. Lastly my GTX 480 Hydro has never died or thrown errors despite its FTW overclock and insane power requirements, but it has a lifetime warranty so I run F@H on it to heat the kitchen in winter.
I never said you're guaranteed 2-3 upgrades, it's simply my opinion that if you buy a flagship card and use it for ten years, two is certainly reasonable. Particularly if the card is run 24/7 for folding, crunching, or mining. Again you're taking the gamble buying the warranty, if it was a surefire 3 upgrades EVGA wouldn't offer such a warranty program. But after having my GPU blow itself up after 2 years, having a guaranteed GPU replacement for the next ten years sounded fine by me so I took the gamble. I also happen to run my cards 24/7 Folding, gaming, or doing whatever. I also have moderate overclocks on them, so I've hedged my bets.