Hmm... I practice my guitar alot, and I don't get calluses.
You've probably been playing so long by now, that your fingers have gotten used to the indentations from the strings. You usually get calluses when you just start playing.
I've played Piano/Keyboard for 6 months, Alto Saxophone for 1 year (don't know how many months :/), and Guitar and Bass guitar. I'm not so good with the Bass or Guitar :/, but I'm good on Piano and Sax.
