Pistol Whip (just came out) seems to have nailed it pretty well - https://www.youtube.com/watch?v=Bae9EykifVk

Not sure it applies to FPS, but nausea in VR first person continuous movement almost completely disappears after 2-3 hours (over a few days) of gameplay on lower turning speed.

I played Fallout 4 like this a bit, and my wife spent nearly 100h in Skyrim VR.

I watched on youtube some Fallout4 and Skyrim gameplay and the player after adjusting some of the options seemed to enjoy it a lot, a few hours of playing seem possible for an average gamer after getting used with the technology.

I played a stationery FPS vr game and it’s certainly a weird disorienting feeling. I also get motion sick pretty easily. That said it didn’t really effect me much outside of a little disorientation.

In some games you can at least move some meters around if you have roomscale VR. But for every bigger movement than that you have to use teleportation.

No, you just need to get past the initial 2-3 hours with breaks while your brain adjusts.

easier said than done unfortunately

The most popular game by player count is Pavlov VR and it's full movement via left hand C-stick. I play for hours at a time comfortably.