I did a trial with the soft paws (but only on the front feet). I did 5 cats. 1 cat kept them on for the full 5-6 weeks. The others lost them one at a time making it a real pain to replace 1 (or 2) a day. Some were even lost within a day or two of being put on.

They only come off as the nail sheds it's outer layer. So it depends on how often your cats sheds this outer coating. And all nails don't shed at the same time (as I found out).

You no longer have to buy them at a vet. Pet stores of pet catalogs (online, too) sell them now.