There is no single lifespan
A slipper worn for an hour on carpet has a different life from one worn all day on tile, stairs, decks, and driveways. Construction, fit, frequency, floor surface, moisture, and care all affect wear.
A calendar promise would ignore those differences. It is more useful to watch the sole, seams, fit, and lining.
Wool compression is normal
Natural wool starts lofty and settles under repeated pressure. A flatter footbed does not automatically mean the slipper has failed.
The more important questions are whether the foot still feels secure, the lining remains intact, and the sole continues to provide an even base.
Fit changes the wear pattern
A slipper that is too loose can slide and rub at the heel, binding, and toe. One that is too small can place excess pressure on seams and compress the lining unevenly.
Choose a gently secure initial fit while allowing natural wool to settle with wear.
Use the sole for its intended routine
A practical hard sole can handle clean household floors and occasional dry doorway steps better than a soft sole. It still wears faster on rough pavement, wet surfaces, and repeated outdoor errands.
Keep comfort slippers away from weather and terrain they were not designed to handle.
Drying and storage protect the complete slipper
Let the lining dry between wears, address small marks early, and avoid direct heat. At the end of the season, store the slippers clean, fully dry, and lightly supported.
Replace footwear when the sole is uneven or damaged, seams open, the upper no longer holds the foot, or the slipper cannot be cleaned and dried safely.