So, let me see if I get this straight:
1. You own an EVGA 1080 FTW card
2. It's been running great for you and you have no issues
3. You are concerned that there might possibly be a future potential issue that maybe might appear
It's not in EVGA's (or any company's) best interest to knowingly sell bad hardware.
Why would EVGA (or any company) honor a warranty claim to the tune of "I don't have an issue, but I want a new/different card because there might be one potentially in the future"?
It's EVGA. If there is an issue, they got your back. EVGA is known for going out of their way to keep their customers happy.
As I see it, you have the following two options:
1. Sell the card and buy a different one (you will get less than what you paid for it...it's used hardware)
2. Enjoy the card. If anything happens, EVGA has your back
For reference, I own an EVGA 1080 FTW card. It's been running folding @ home 24/7 since I got it back in July. I am not concerned.