Campaign World - Distances?

[the Jester]

How much thought do you put into the area/scope/distances of your campaign worlds (well, for homebrews, I guess)?

Do you focus on a small(ish) island? Somewhere on a continent? Plane-hopping? Do you just draw a map and worry about distances later?

My world is not a planet, it's much bigger than earth. This is so that there's always somewhere I haven't detailed yet, where I can start fresh.

The 'core area' of the campaign stretches about 5000 miles across, but that's for epic pcs. The halfling mid-level party I run is currently interested in an island about 400-500 miles long.