I just found that when I stole Jezebel's Cloak, the timer reset to 3 regardless of how many turns were left.
I opened Trainer and tested Sundial, Cloak, Dimensional shield and Wings. Sundial and Cloak both had their timers reset when stolen (stealing your own did not reset the timer, however). Dimensional shield and Wings did not have their timers reset.
I don't recall this happening in the past, but I could very well be wrong.