A genuine hakko lasts a long, long time until I drop the iron or mangle the tip in some accidental forceful way. Can last through 50lbs of solder rolls if I am super careful. I usually replace when they get a burr and start scratching the PCB material.
I don't use wet sponge to clean. Just the metal shavings stuff. Also have a bad habit of flinging excess solder with burn flux off the tip into a trash can.