We break ours down to 1000 per page. A simple setting in Yoast SEO - if you decide to use their sitemap tool. It's worked well for us though I may bump that number up a bit.

I can tell you what we do. With over 35 000 posts we are always tweaking the better ones and dropping the dead weight. I'm currently going through a bunch of posts from 2010. I run two quick tests on them - I check the PA [page authority] on Moz. If it's 1 then that's one strike, anything higher I consider working on the post. Next is a quick check in Google Analytics for traffic over the past 6 months. As you can imagine many posts from 7 years ago have 0 traffic. This is strike 2 and in my ballpark, 2 strikes means 'you're out!'. I delete the posts, a hard 404. As we cut the driftwood from our nets I feel we will be more efficient  at catching more fish.