Obviously there are some last minute connections that work out but I would say that for some the more time to make a plan the better. Anticipation is exciting too. I have recently started making arrangements three weeks in advance of a trip to San Antonio. Nothing definite but just initial contacts once I knew the trip was definite.
I can only speak for myself, but I usually plan my hobby activities weeks, sometimes months in advance, especially for repeats. Impromptu spur of the moment for me is a day or two. So a month is not too early, especially since it seems the ladies tend to visit all at the same time.
I have given notice of a trip anywhere from 2 weeks to 2 months. I find that the more notice, the better reception I get. Some guys like to plan ahead, and for others, their schedule may not allow for that. It helps though, if you have enough solid pre-bookings to cover your overhead for the trip. No lady likes to take a gamble on that.