I think it's different for every person. You mentioned you only listen to about 1 lp per day. I consider myself a moderate listener and easily listen to 3-4 a day. I bet there are plenty of people here that listen for 5-6 hours or more.
Also I think it depends what genre's of music one is interested in, and how and if thier tastes are developing. I had amassed probably 2500 or more rock LP's and then became more interested in Jazz. It was as if I had to start collecting all over again. I have a small collection of classical, but who knows, I may someday feel the need to fill that out as well.
At this point I probably have 4000 LP's. I am out of room to store them though, or I would be buying considerably more. Looking at the catalogs of new pressings and releases, my mouth simply waters. We are clearly living through the LP's renaissance. The pressings (new releases and some rereleases), cartridges, tuntables and phono stages are the best they have ever been, even when the LP was a mainstream format.
LP playback is simply so good, I hardly ever listen to digital anymore, and can often get new releases on LP rather than CD. I probably should follow your lead and pair down my collection from duplicates, and LP's I won't listen to anymore. That would give me the space for new acquisitions.