Ease of logistics is a big one for me too. My ideal tour is a loop from home. Otherwise, the destination needs to be very special to get us to ship the bikes. Like a month or more on a different continent, or crossing this one.
Of course a safe route to cycle is at the top of the list. I agree with looking at resupply points.
Temperate weather and favorable prevailing winds are up there. I often pull the trigger on a short ride at the last minute to take advantage of a good five-day forecast. I may plan a loop direction based on a predicted wind shift on day three, for instance.