Doing a coolant flush every 4yr/80 000km is good for cooling system longevity. Overtime the coolant becomes acidic, and wears down seals such as the one in the N5x water pumps.
Fuel injector flush, I'd hold off on. If it was a 335i I'd say the carbon build up may be enough to call it.
For reference - we offer our coolant flush service, with original BMW coolant for only $82.40+ tax. That is for all BMWs.