Tattooed eyebrows last between 6 months to 3 years.
Unlike regular body tattoos that are permanent or at least permanent until you have the tattoos removed the eyebrow tattoos are not permanent and need periodic touch ups to keep the eyebrow tattoos from permanently going away.
Usually after 6 to 8 months you need to go in and have your eyebrow tattoos touched up to keep them.
For some people a touch up of the eyebrow tattoos are needed after 4 to 6 weeks if it starts to fade sooner.
So at least if you get an eyebrow tattoo and decide you don't like it the good news is that it will eventually fade and not need professional tattoo removal like other body tattoos need.