About eight years. I really think, somehow, your intelligence comes into play in graffiti. It seems like I never see drooling idiots with talent. Most established writers:
a) have been writing several years (Most worth looking at, at least 7. With the exception of Die.)
b) don't speak out of their ass about sibjects they have no knowledge of. (Meaning anything at all, not graf-related)
c) Have a sense of humor.
d) Speak their mind.
e) break the mold of typical graffiti ideals.
f) don't run around spouting "Graffiti should be legal! Marijuana makes you graf better! Fuck whitey! Graffiti is ART just like everything else"-
g) realise arrows are unecessary at best.
h) Won't have to read anything I've written here.