Using LCD with multiple shields...no pins left

each character will use around 75us of time for
a total of around 6ms of lost CPU time to fully refresh the entire display.

That figure is highly implementation dependent.

Of course if you look at the full quote --> "If using FM's library and 2wire mode with a SR, each character will use around 75us of time for
a total of around 6ms of lost CPU time to fully refresh the entire display." <-- it is quite clear that he did specify the implementation.

Don