Since 1993 full-time professional S5 and later S7.
Nearly 20 years now...
btw. nice thread!
Oh dear, I don't even beat you in the absolute number, not even talking about different scale...
Anyway, it's 18 for me, 18 months that is.
Before that I had some very brief experience with programming something like PLC in assembler, but mostly nothing really related (except perhaps for the part where I can laugh about anything in the primitive HMI used programming language (well, it feels really like laughing in the face of programming to say that) - VBS).
So there's no wonder everyone knows so much while I barely can tie up my shoelaces.
I don't see why people would still care about travelling salesman problem nowadays. You can simply buy stuff on the internet.