How long it takes me to properly absorb something depends quite a lot on the music, its complexity, accessibility etc. But 3-4 listens is pretty much always enough to know roughly how much I like it, enough to be able to rate it anyway. And particularly in this roulette, I don't really want to "properly absorb" these mini "best of"s, I want them to introduce me to the artist's music, get me interested, and then I want to check out full albums and really absorb those that I like the most.
I admire (and am jealous of) Rich for being able to tackle that amount of music.
I don't think it deserves admiration, I think it's just different ways we approach/consume music - neither better nor worse.
I do have the benefit of time during which I can have music on, which allows me to listen to a lot (though not unlimited, which is why I capped players in my album roulettes and have capped length in this one).
And in terms of my approach, I find albums or these mini greatest hits easier to track and get my head around than if I'd received individual tracks. I like being able to consciously select a new artist/playlist and absorb their music for 12-21 minutes, then select the next one, and so on. If it was all individual tracks, I'd have to either do that every track, or put them in a big playlist but then it's very easy to tune out and miss a submission entirely.