I don’t know about thousands, but I get the impression some of Beat Saber fans have hundreds of hours in that game alone.

Just like with non-VR games I’m sure there’s a lot of variation. Some titles are designed for long branching narratives that invite replay. Some are inherently multiplayer and get most hours from that. Some have endless modes you can play over and over to best your high score. And some have none of those things and just a single definitive ending after 5-20 hours.