The stock one can be repacked with grease at 100K and maybe go 150K miles but it's easy to replace it too. The idler seems to last longer, it can also be repacked but it's pretty cheap and at 150K or so could be replaced and be done with it.
Note: I do not know if the replacement pulley I suggest works for the PFL, never tried. I know the idlers are different 32v vs 40v.
If you repack you only use a few blobs of grease, it has to spin without dragging through the grease once it's initially pushed the grease out of the way.
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