As discussed on PPR before it is BAD PRACTICE to issue taxy and R/T instructions during the high speed part of the landing roll unless there is some sort of problem. Before or after, fine. Pilots are actually not still doing the crossword at 100kts on the runway.
You want me off at alpha and it is not in the airfield briefing - tell me at a decent range on finals so I can review the landing performance and re-brief if necessary. On the roll, the chances are I may ignore it and exit where I have planned.