Campaign maps rarely stay pristine, and that is part of their charm. The useful version is the one that can absorb discoveries, corrections, rumors, and consequences without collapsing into noise.
Separate permanent geography from temporary information. A light notation system for dates, factions, routes, or session references can keep changes understandable long after the night they were added.
The page should leave some unclaimed space. Empty areas are not wasted. They are room for the campaign to happen.