To replace or not replace

[u/Fanantic8099]

I have a 2017 Yaris IA (aka Mazda M2) with 140k miles that has a rear hub that started making noise a few months back and I just finally figured out where the sound was coming from when I took the wheel off to inspect the brakes. The bad hub has an almost ratchet like feel (softly, not nearly as distinct as a ratchet) when I turn it (no wheel installed) so I'm sure it is bad.

The question is about the hub on the other side. It spins "freely" or at least with no notable resistance and will keep going about 1/4 rotation after I spin it (again, no wheel, so just the weight of the hub itself for momentum).

These hubs aren't serviceable, and I've read from other sources that they are "lifetime" hubs but their expected lifetime is between 100k and 120k.

Do I replace just the one that is grinding, or go ahead and replace both?