Consider an "unoriginal pawn move" to be a pawn move whose notation matches a move already played in the game. For instance, after 1.e4 e5 2.d4 exd5 3.e5, there is one unoriginal pawn move, the e5 played by white. If e5 is played again later, that would be another unoriginal pawn move.
(For clarity, "e5+" would be a different move than "e5").
How many unoriginal pawn moves can be played in a single game (assuming all standard rules, legal moves etc)?
[originally asked as part of this question]