I am finishing up my MS in aero right now, going to school while working full time. None of my classes were available online, and I also live an hour+ from school. At first I took one class a semester, but I ended up moving to two a semester to get done sooner.
If you are going to go back, I'd recommend taking 2 a semester right away and get done asap. I was a good student at first, but as my responsibilities at work increased, my time for school decreased. Also, if you can't find any online classes, you had better enjoy driving. I do, so the commute never got to me (130 miles a day on school days), but I know a couple of other people who hated every second they were driving home from school.
The kids in my school's MS program are all full time students, so during the school year they had plenty of time for classwork. And, professors adjusted homework due dates and difficulty based on this fact; so, there were a lot of times I had to take days off of work to get the homework / projects / etc done on time. And, it was nearly impossible to work with other students on homework or projects, because they all did homework together during the day on weekdays at school, and I did homework at night and on the weekends at home.
I'm not sure what your living situation is, but if you have a spouse and / or a home, it's even more difficult.
But, I think there were a lot of advantages. I learned a lot, which is to be expected, but because I had work experience, I was constantly ready to apply what I learned to my job. Since a lot of the other students had not worked yet, they still did not have the feeling of how all of these facts fit together. Also, I had the advantage of learning a lot of 'classwork' at my job, so when I saw it again in school, I knew it already and was a step ahead of the rest of the class. And, from my perspective as an aero, I felt like I hadn't been taught enough in my undergraduate days, and the coursework for the MS really answered a lot of questions and filled in a lot of gaps for me. And finally, there's the rewards in the working world-advantages of increased promotion potential, more money, etc, etc.
Overall, I'd recommend it. But, I would have started out taking two classes right away a semester, instead of one.