So I've started, as Brandon Sanderson would call it, discovery writing an Urban Fantasy where my MC is a recent college grad, and in about 3000 words has dropped the 'F' bomb at least 20 times. I don't know that it's too unrealistic, considering character and setting, but I'm worried that it may not exactly be readable dialogue. Which got me thinking about the question: How much swearing is too much?

Realistically, I have friends in their mid-twenties (the age of my character) that use profanity the way other people use filler words. It's to the point they stutter if I challenge them to not swear when they speak. So anybody have any thoughts on guidelines for how often to pepper dialogue with profanity while still keeping the book readable?