I purchased my Z from the original owner in 2001, with a blown engine and 90k miles on the chassis. I put 45k miles on the rebuilt engine (and same injectors) since. One good tidbit of info is the fact that my Z was never garaged, and it sat outside under a car cover for duration of 5 yrs without being driven.
Maybe it's the weather. Maybe it's the gas. Maybe I'm the luckiest person in the world. Maybe I've been running on less than 6 injectors. Who knows?