Rough plans at the beginning of the year, like "1 week to go to this place in July-August timeframe" so I can plan time away from work accordingly.
6+ months out for international travel for best deals on airfare.
Day of for weekend trips sometimes. Or tacking on a day or two to the end of a work trip.
Years out for sporting events. Like the 2031 rugby world cup will be hosted by the US and I plan to go to quite a few games, plans will develop as cities are picked and pool play schedules made.