Clearing a recurring blockage without surveying the run is treating the symptom. The pattern to look for is timing: if it returns within weeks or months, and always in the same location, the pipe itself is the problem.
Common culprits are a dropped joint after ground movement, roots entering through a failed joint, a belly (a dip where the pipe has sagged) that holds standing water and silt, and scale build-up narrowing the bore in older cast iron.
The fix is to survey once, identify the defect, and repair it — usually with a patch liner. That ends the cycle of paying for clearance three times a year.