Constantly, to the point that they would be raw and red the next day. Since a friend had found her abandoned in a box at the airport, I figured it was an attachment issue and never stopped her from licking. I decided she must need to do it for security and that she would grow out of it. Plus I am a cat person. I have never minded a cat's dainty sandpaper lick.
Dogs are another story.
A dog is lucky to get in one swipe before I push his tongue back in his mouth where it belongs and run screaming for soapy water. The cat also liked to lick my daughter. She, too, felt as I did and didn't mind. But my husband and son thought it was revolting. So they would always shoo the cat away when she took a mind to start licking them.