i have permanent eyeliner and love it. its the subtle lash enhancement type. not a bold line.
my mom is a permanent make up artist with many years experience. if you have any technical questions or want a rec. for someone reputable in your area she would be happy to help.
you can read the permanent makeup f.a.q. here if it might help answer some of your questions
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pm me for her business ph. #
i think the key is to go to someone with lots of experience in application and sanitation. also, you have to go through their book of before/after and make sure they do the style you want, not just that they said they can do it.
also, its better to do less than you think you want the first time b/c its easy to add more later but going too heavy the first time can make you very unhappy.
make sure they use the highest quality pigments and their work area should be spottlessly clean. do they listen or do the hard sell? do they offer topical anesthetic? [i highly recommend it]
like regular tattoos the pigment will fade some over the years and people may need touch ups after 7-10 years. a lot depends on things like how much sun exposure do you get on the pigmented area. a good quality pigment shouldn't change from brown to grey, but over the years, the brown might fade in intensity.