[jacquesm]

One thing is for sure, if you don't go back to studying now chances are you never will.

And whether or not it will be useful to you is very much depending on your future career path, if you are looking forward to continued employment in that field than an extra degree certainly won't hurt, if you plan on going entrepreneur then it is of much less value (though for sure you'll benefit from the networking opportunities that come with a large university).

Five years of experience and already a third of your BSc in CS, you might be able to do it 'on the side' but that's really an exercise in self discipline.