Yes I have, it's only possible if you're particularly obsessive with a composer or two. People say life is too short to focus on one composer, I'd say life is too short to spend it on other composers you're not really interested in.
I want to get all of Chopin's music (that I love I guess, not all 200+ works) because he's my absolute favorite. Over the years I've exposed myself to a bunch of composers, from the ones in the standard repertoire like Bach, Beethoven to more obscure ones like Liadov, Stachinsky or Medtner. Regardless of all that for some reason Chopin remains the closest to my heart.
I want to get all of his large scale works that I adore under my hands, to the point I can play any of them whenever I want wherever without any sort of prep work whatsoever. I spent the majority of 2021 working on learning his entire set of preludes, some etudes, polishing his op. 52 Ballade, learning the op. 23, a bunch of mazurkas and nocturnes. I played a little bit of Scriabin and Rachmaninoff here and there but that's pretty much all I did for an entire year. Mostly Chopin.
And I *** love it. I'll do it again this year as well. I don't feel like I'm wasting my life or whatever focusing on the one composer I truly hold dearly to my heart.
The goal is all of the op. 10, op. 25, and op. 28 sets. Most nocturnes (some of them are boring), about 20 or so Mazurkas, all Ballades, all Scherzi, Polonaise Fantaisie and Op. 53 (already learnt op. 44 and polonaise brillante), all waltzes, all impromptus (no 2 and op. 66 are left), and polishing op. 60 which I learnt poorly several years back. After I'm done with that I'll feel "relieved" and focus more on other stuff.
I definitely see myself spending an entire year on Liszt and Ravel in the next 5 years. Especially for that B minor Sonata!