I have 'fasho' tatt'd on my inner lip.. I got it because it's an inside joke, and it's faded, but you can still read it... after 2 years, most of them should be 100% faded. A lot of tattoo artists won't do it as it is pretty much a waste of ink & money & time. If it fades any sooner, the tattoo artist didn't do it right at all. they are supposed to last 1-2 years but can last only about 6 months in some cases. it depends on how you brush your teeth, if you drink soda or any other drinks with acid, alcohol, etc.. My grandpa is a dentist and he's was really pissed about it, just like tounge studs, dentists don't like anything around your teeth & gums....and it didn't hurt, but none of my tattoos hurt me, it just feels like a hot prick the whole time.