When I start practicing tomorrow, it'll have been 6 days. That's the longest I'd gone without playing since I started taking lessons in January. I plan on using this time for a little bit of retrospection on how I practice.
From week to week, I find that I work on the things I learned in the last week's lesson, work a song or two for next week's lesson, and then play through a list of songs that's slowly been getting longer.
I've reached the point where I've got more to practice than I can fit into one session though. Instead of doing the same session every day for a week, maybe I ought to be planning out a whole week's worth of practice. This way, I can go back and make sure I'm touching on old songs and skills that I'm not currently working on.
The tricky thing about practice isn't doing it-- it's planning it. There's a saying that "perfect practice makes perfect." Getting perfect practice involves putting the time in to planning perfect practice. There's not much point in learning new skills or songs if they just fall away after a few weeks. In the coming weeks, I'm going to work on outlining my practice for the entire week to make sure I'm rotating old skills and exercises in with the new.