Many different factors play a role in the lifespan of the implanted pigment. 
Clients skin type plays the biggest role in longevity and the general outcome of the procedure. Oily Skin types hair strokes may heal softer with a powder finish while drier skin types may heal more crips and defined.  Darker pigments tend to last longer.  Proper UVA/UVB protection will prevent colour from fading as quickly when in sunny climates. 
Aggressive skin treatments such as laser, chemical peel, dermabrasion etc. do not get along with micropigmentation.