Haven't bought a card that wasn't Nvidia in a very long time, I think the ATi 4870 was the last one before jumping ship.
Since then had a 460, 670, 970 and now the 980Ti. That's 5 cards in about 8 years. Like you though it was the 670 that had the most mileage, must have had that about 3 years, fantastic card. I'd have had it longer but a mate was interested in buying a PC so I sold him mine and put the money towards my next build.