Hi Angela,
However, it always intrigues me when this question about 18 hour TAFs arises as to what exactly the pilot wants to do. This topic is in a GA forum and the range for most GA aircraft is under 5 hours. This means the pilot will have to land to refuel most likely well within the validity period of the 9 hour TAF. And once landed the pilot can look up fresh data.
Just a guess, but I think its because most of us have a mobile (actually I dont have one, but SWMBO does) but not all of us laptops and internet connection to go with it when visiting somewhere. Personally I find that I need to plan the night before if I can fly somewhere, not just for having a plan for myself, but usually for the person the other end I will be seeing/visiting....And I fly only for fun and can be very flexible.
TV weather isnt really good enough is it?
Regards, SD.