@Fatberg - sounds very similar to what I do but I don't purge. I tend to save albums as playlists.
I have a master Discover Weekly playlist with every Discover Weekly song I've been recommended going back to around 2015 I think.
I also hit the + button on songs I like. I'll then visit my 'Songs' list and visit the artists whose songs I've saved and listen to their catalogue more deeply. If I like an album of theirs, I'll save that as a playlist. Think that makes sense.
I tend to only save albums or playlists I'm listening to at the moment on my phone, along with the 'Songs' playlist. It's about 2000 tracks in size at the moment. Oh, and my Discover Weekly. It means I have 30 new tracks to listen to every Monday morning which is nice. They download automatically overnight.