Fuel injector replacement, needed at what mileage?

[Factory6speed]

I just did new Bosch ones on my E36 m52, not cheap.. Once in a while it would have a little hiccup at highway speed, like an injector wasn't firing. The number 4 one was pretty carboned up and clogged, actually all 6 were a mess but #4 especially was different. I removed the original 1996 fuel filter back last March, I'm sure that had a lot to do with it. 156K miles.

I think they are still good, and they don't make these kind anymore, the large pink ones. I will be sending them out for the rebuild service. Race German offers that I'm going to try them. The car is running amazing, but I did about 75 other things at the same time so I can't say how much of it is due to the injectors, I'm sure it's part of it. Expensive but nice to get out of the way.