I find that I do the same as you -- I learn enough to get whatever job I'm working on done. Now, I try to take the time to do some research so I don't write too crappy of code, but there are those times when you come back to something you wrote a few months (or a few years) down the road, and you realize just how bad the code was that you wrote, given what you now know.

As for being self taught, yes and no. I've taken basic programming classes (although my undergrad is in civil engineering, and my current master's work is in library science) I've taken classes in Basica, Pascal, C, C++, 68k Assembler, just because I felt like it. Fortran (back when it was still FORTRAN) and Logo, because they were required for school (okay, one was elementary school, but still). And one of my past employers sent me to learn PL/SQL and CFScript (well, ColdFusion in general).

But that whole 'self' taught thing is really hard so say what qualifies as 'self'. I've learned a lot from people I've worked with over the years. Even if they're not teaching you directly, I never would have gotten to my current point without help from others when I learned Perl, VBA, LPC and k?sh. I guess the only ones that I'm really self taught in are those that I don't really use that often (ie, the ones I suck at), like AppleScript and Java. Well, I guess I can get by in JavaScript, and I've never had someone to apprentice to or had formal training in it... just books and websites.

As for keeping skills up to date, I get that from using them, or reading books, for the most part. My current employer has a training budget for me, but I don't find that training is worth it unless I can immediately apply it to what I'm working on. If I don't get the change to use it, and burn it into my memory, I forget it rather quickly.

I've never had any classes in general programming theory (I thought about taking a class on data structures once, but they required you to take Ada first, so it wasn't worth my time), but tend to get that sort of stuff from books for the most part. To some degree, it's actually helped me, as I (used to, less so now) approach problems from a different direction than the folks I worked with who were trained as compsci.