I agree with Carl that bed leveling should not need to be done regularly. You should identify the cause of unstable bed leveling so that you can get consistent print quality.
In my experience, depend on the model of printer, the problematic part can be different. For those printer with dual z-axis, z-axis squaring before bed leveling are critical to achieve stable bed leveling. Unstable bed leveling can also caused by loosing z-axis endstop mounting and bed leveling spring pressed too tight or too loose. You can identify the best bed leveling spring by adjust the combination of z-axis endstop and bed leveling screw. Addition of 3D printed spring cups also helps for those don't come with spring cups.
The bed adhesion method also impact the stability indirectly. If you have to use strong force to remove the print, then it is hard to make the bed leveling stay the same. In my experience glass bed + glue is better than blue painters tape for example.
Put your printer on stable and leveled surface may also help. The vibration of the printer frame and movement of y-axis while print at high speed can also impact the stability of bed leveling.
I don't think there are anything wrong with the mechanism of auto level feature in Repeitier and Marlin, it does not work well for many people often because the calibration is off or reproducible measurement issue with low quality distance/pressure/proximity sensor, I don't think NASA will send cheap 3D printer to mars due to cost concern.
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