I'd hope for 5 odd years, maybe more.
I found that with my Galaxy Note 1 and Galaxy Note 4 they started to grind to a halt around the 2 year mark (which would coinside with a new contract).
I actually bought the Note 4 and went SIM only, but was really disappointed with it's performance in the end.
I've now had the Google Pixel XL for nearly a year and a half, and the performance is as good as the day I got it. There is literally no reason to replace this superb phone. I guess only the battery failing would make me consider a replacement.
And to the Apple guy, the support for the Pixel is second to none. You go to the support section on the phone and there is some real person ready to chat to you. It's most impressive.