I'm not sure of my mileage because I popped the speedo off for as desert race sometime back and haven't bothered to put it back.
But my neck of the woods is on the edge of desert country. It's dry and dusty for most of the year. I cleaned the gas tank and changed fuel filter maybe 1k miles back, but with an injector I think it's more about super fine dirt particles that can pass thru the filter. The dissolved stuff that will end up being part of the varnish on the injector.
It also depends on the contaminants that are in the pump gas when you buy it.

Because I'm a carby centric kinda guy, the removal was more an exercise in learning the process so I can do it quickly and efficiently for the future. That being said when it was all off I wasn't not going to spray some contact cleaner and compressed air thru it.

As to result? Smoother throttle response and idling even with my quick clean process. Makes me think maybe a sonic clean will make a really big difference.

As I mentioned, from now on when I'm servicing the bike, the injector will get a service as well.