Stoner - I go to evening classes 2 nights a week - dosbarth cymraeg (that's welsh language class in case you need a translastion )
I do find it hard, especially as I work (more than) full-time - usually get back from work in a mad dash, drop work bag, grab welsh class notes, and fly out the door. Get home about 9.30 / 10 pm hungry and tired. Plus, I need time to fit in doing the 'homework' that goes with the course.
But ... I'm doing something that i'm interested in and committed to (as I live in North Wales, I personally find it pretty important to be making an effort to learn to 'siarad cymraeg'). Plus, most other people in the class are in the same postiion (ie usually knackered), and its often good fun. I'll be doing classes 2 nights a week for probably at least 5 years, so it's a long-term commitment.
I'd recommend going for it, but only if you're feeling committed to whatever it is you are wanting to do classes in. If it is something you are just casually interested in, then work / family commitments will probably mean you'll drop out sooner or later.