I bought a refurbished pixel 5 about 3 months ago! It’s been working great so far, basically new condition when i got it. The battery is better than my last phone (Xiaomi mi 9t) in it’s last days, but i have no idea how it compares to when it was new. Pixels seem to have great after market OS support, so I wouldn’t worry about it not being supported in the near future. I installed Lineage OS right away and it works like a charm. Let me know if you have any questions!
I’m used to 60Hz screens, and i don’t really notice the higher refresh rate. It’s maybe a bit smoother when scrolling, and I think it’s pretty consistent between different apps. I might make a little experiment where i turn it down to 60 for a day and see if i notice anything!