I have (and may do again) :) Started as something interesting to do/use my brain as my DD got older and ended up going to Universty

Didn't anticipate it but thought what the hey, great experience :-D
OH has also gone down the same route and is now an Adult Ed Lecturer/Tutor. Still attending classes as well to increase his area of expertise. He's also become a Luthier in a similar way, but more intensive professional courses ;)
His students are very varied - and depends on subject too, some are there for fun, some more serious.
What is it you want to know?