Only 30 years? Working at Channel Islands National Park, I used topo maps that were produced in 1943. .The basic topography from that era is still in use today, more than 70 years later. Using them routinely from 1982, I found that the topography was usually spot on. Not so with cultural features, but that is why you carry a pen and pencil.

Interestingly, although the islands held still for their photos in 1943,the maps show nothing of the military camps and fortifications that existed at that time.

This situation is true for a lot of wild spots, at least in the western US.

The very best thing to have is good, sharp copies of aerial photographs. They typically are date stamped, and even for out of the way places like the Channel islands (US)there is now a plentiful selection.

The best map of the Channel Islands NP is National Gepgraphic's Trails Illustrated #252 - Channel Islands National Park. It is current on both topography and culture, but is still essentially the 1943 aerial photography. This is probably the case for many areas in this series.

You can never have too many maps/photos....