CJL: How much progress in 1 year?

I'm looking to go to Japan to do the CJL program for a year, and am wondering how much I can progress in 2 semesters (I'm ambitious). If you enrol in say Comprehensive 1, do you do that the whole semester, and only progress to Comprehensive 2 in the next?

I've studied Japanese on and off (combination of languages school and self-study) in my youth and had passed the JLPT N4 by a pathetic 4 points lol. So I have a lot of basics down but also a very shaky foundation. Plus that was over 10 years ago (I'm in my 30s).

I feel like I should rebuild my foundation by starting at Comprehensive 1 but completing only Comprehensive 2 by the end of the year doesn't feel like a whole lot of progression.

Keen to get some advice here!