Must admit in LVPs it is very annoying when an aircraft reports vacated when the nose wheel has just started to turn off the the runway centre line. A lot do it or report vacated when the flight deck has just passed the CAT 3 stop bar. Never mind the other 175 people behind!
On normal ops when you aren't going to stop report vacated when the back of the plane has passed the physical edge of the runway 'cos then we can use what is termed 'anticipated separation'. Sounds dodgy but all the busy airports, and some quieter ones when it gets really tight, use it all the time.
HTH