Fuel Injector Problems.

[Judd 944]

I had a check engine light come on about a month ago. I had a Cylinder 2 Misfire, Injector 2 Circuit open, and Multiple Misfires Cylinder 2. I changed the sparkplug, swapped coils, and checked for voltage on the connector. Listening to the injector I could tell it was not "clicking" I replaced the injector and it worked fine for about a week. this moring my car was running rough again. I "listened" to the injectors right away. Cylinder 7 was not clicking. sure enough the check engine light came on. Cylinder 7 misfire, Cylinder 7 Injector Circuit open, Multiple Misfires Cylinder 7. Is there something larger causing this? I dont want to keep changing injectors every week! Are fuel injectors common to fail? Oh, is it ok to drive 400 miles on 7/8 cylinders?

98 (jan prod.) 540i Sport
94k miles