My front passenger-side blinker is working about 1/3 the times I use my X5...when it fails, the dash tells me "Check side lights". But if I set my alarm, the failing light flashes twice. Somedays it works, somedays it doesn't

I was under the impression that light bulbs either work or don't...it's not something that dies a slow death.

I don't want to go through the hassle of replacing the bulb if it's a bigger problem...anyone have any experience with this issue?