RE: At my wit's end with Y-layer shifting
As the Y axis bearings wear, they will begin to rattle and buzz inside their cases. It gets annoying, and the bed also has a rotational freedom that can't easily be controlled. I solve both the rattle and rotation by adding a strain force to the rotation : a 6" rubber band between the left front corner of the bed and the right front corner of the frame. Quiets it down and ensures the bed is always running on the bearings with a preload, and not flopping around.
To this end, I've run the life expectancy of typical LMU bearings on a 3D printer like ours ... I am NOT impressed. One manufacturer states life expectancy of their linear bushings as 50 kilometers. On a Prusa MK3 printing a 210 mm square box at 35 mm/s, that's only 198 hours. lmao. What a bunch of Whoop Arse.
Printing smaller things extends those hours a bit, but not by a large margin since there is a minimum speed the printer obeys... so to be gracious, bearings are officially worn out at 250 hours. If I am very generous with loading factors, we might get 4x that value.
Not surprisingly, that 1000 hour estimate is about what I am experiencing on Y before the bed starts doing odd things.