As long as you don't have something like auditions/competitions coming up, I don't see any problem with doing that. Last year I worked pretty much like that- concentrating on Bach for the first third of the year, then on Chopin's Mazurkas, before I started preparing for auditions. The result was a much deeper understanding of both genres, which I don't think I could have obtained if I hadn't delved so deepily into them.
If you're planning on studying music in uni/conservatory, however, make sure you don't let your repertoire get too lopsided!