I've owned these slippers for 18 months.  With moderate use over this time, the sheepskin lining is wearing through at the heel and ball of the foot -- on one slipper, there are two patches of half a dime size in which the lining is gone, and on the other slipper, the lining at these two points is barely holding on.  This is a typical problem with sheepskin -- it mats down quickly and then wears off.  Other parts of the slipper are still great and it's plenty warm (the sheepskin on the top and sides is still thick).  The slipper remains comfortable for now, because even without the sheepskin lining, the sole is cushiony and forgiving.  However, I suspect it will need replacing within the next 6 months or so.  I expected more longevity for a rather pricey slipper.

Another important note: after you receive the slipper and start wearing it, the top of the slipper will immediately develop deep creases, such that it's appearance will resemble the folds of the face of a Bulldog or Shar Pei (I assume this is why the slipper is called "Old Friend" -- it resembles a dog).  Personally, I'm okay with this, but you should note that it will NOT keep the smooth surface shown in the picture.

Overall, it's worth 3.5 stars and will consider buying this slipper again; however, I will be looking more closely at other options.  The strap is great and they are definitely comfortable (though considerably less than they were new), but the lack of durability at the pressure points (heel and ball) is disappointing.