If you already have a job in the tech field AND you have a BS in anything, I'm not sure if there's ever a good time to get a CS degree.
Posts above mentioned 4 years and $20k. I have a CS degree and it was more than $20k each year (10 years ago) and I can tell you that as far as coding is concerned (or techniques/practices that you could use as an application developer), CS degree teaches you very, very little. I've seen people graduate with having written almost no code.
I've worked full time since 2nd year of college till I graduated and work experience (along with really good mentor) taught me 1000 times more than the degree. I went for the degree because those two letters "B.S." on your resume let you get past the "HR filter" in many companies.
If you are looking for a job or work in academia where actually knowing/using CS theory is important, than by all means, go get a degree. But I've been doing commercial applications development for 12 years now and I can count on my figures the things I've learned in school that I didn't know already and was able to apply to my job (and I wouldn't even need to use the second hand to do it).
Also it depends on your study skills/habits. Some people prefer formal lectures and they don't have motivation to learn and study if there's no exams. Whereas even in school I always preferred to read/study on my own because information sinks in better. So if it wasn't for standard HR hiring practices, I personally don't put much value on my CS degree.