I'm not a banjo player either, but I understand the monotony of practice all too well.
When I first started flatpicking guitar (about the same time that I joined up here), I would select one of Ben's tabs and pound away at it with an enthusiasm that's easy to get when trying something new. I would literally play the same piece of music for hours a day and it's all I would play. I learned a bunch of stuff using this technique, but the most important thing I learned was that I needed to practice smarter.
Playing the same thing over and over wore out my fingertips, cramped my hand, and after a while left me mentally disengaged. Had I continued practicing solely in this manner, I'm sure I would have lost interest pretty quickly. Fortunately, I figured out a system that works better for me.
What I try to do now is make progress along several different parallel tracks. I still work with tabs, but now I'll only work through a piece a few times before I give my hand (and brain) a break and move on to another area. Right now I'm focusing on improving my crosspicking, so I might move on to some crosspicking rolls and when I tire of that I might work on building my repertoire, taking a couple of songs from my wish list (mainly songs that I've heard at jams or on Youtube). Then it's off to something else.
I have a dozen or so areas that I'm working on at any given time. It's more than I can get to on any one day, so I keep a chart to help keep me focused. The big advantage to working like this is that I never get bogged down with practice I don't feel like doing. For instance, some days I don't feel much like singing, so instead of working on repertoire I might work on something technique oriented (like crosspicking), or maybe work through a chapter in a method book, or practice improvising with the radio, or learn some new chord forms, or... well you get the idea.
My chart has grown to the point that I always have a few areas that I'm itching to get to, and I don't find practice monotonous any more. In fact it's just the opposite. When I practice in one area I feel like I'm cheating myself in another and can't wait to get to it.
So I agree with mreiz, do what you need to do to keep yourself engaged and excited about practice. The hours spent holding your instrument pay off in the long run.