Can I just start by saying that typing that title gave me physical pain as I hate missplaced apostrophes (and I sometimes run past a shop called Your's)
That said, is there actually a time when it is a correct use of the apostrophe? I'm thinking of such as
"I have completed your's and your wife's tax returns"
The tax return is owned by both 'Your' and 'Wife', therefore it seems logical to say 'your's' in this instance. Or is my sentence so poorly constructed that I have twisted the rules of English so out of shape that I have wandered into a strange place?