I just turned 20 and I've been programming for 8 years. The biggest thing I learned is that Gates was wrong -- skill continues to increase well after your first 3 years.

Outside of that, programming has proven to be one of the most rewarding skills I've ever learned.

12 - "Learned" Java. Didn't understand any of the concepts;

13 - Learned C, Understood a lot more. Read 'Hacking, Art of Exploitation';

14 - "Learned" x86, Wrote first WEP cracking utility for Win32 (distributed as binary at least :) when FMS was new;

15 - Got down to brass tacks and learned deep x86. Wrote first non-trivial exploit for use-after-free condition in Adobe Reader;

16 - Learned Ruby. Wrote first utility to repack the SSDT in Windows rootkits and hook accesses to the first memory page of the service descriptor. (Lots of people do this now);

17 - Learned a lot of Math. Wrote transfer control protocol on top of IP and wrote a lot of Cisco IOS utilities;

18 - "Learned" networking (A wildly complex and massively underestimated field, I'm not sure anyone really knows networking anymore) Reimplemented all of dsniff w/ STP & 802.1q utilities;

19 - Learned Erlang. Wrote my own NoSQL database (zv.github.com/artifact);

20 - Now :)