I have a generic packing list for each family member. I copy that list into my Excel spreadsheet book for the trip whenever I want to before the trip, and adjust the list as needed for that trip. Example: I don't need to take a fleece jacket when we go next month, so I'll remove that. In terms of the physical packing, I only start a few days ahead. One of the main reasons for that (aside from laundry) is that we have cats and cats+suitcases= the most fun (and fur) ever. I do start a "packing box" about a month before a big trip. It's where things land that I need to take, but don't want to write down on the list, or things that I buy specifically for the trip that I don't want to forget where I put them as I scramble around trying to pack right before the trip. Examples: a new travel fan and ponchos.