I'm glad someone asked this because I wondered the same thing. We will have guests from other cities, arriving at different times and so on. I wasn't sure what the norm is.
I do think that it should depend on what you are including in your bags. If they are bulky then it would be a hassle to pack them and then hope your guests can fit them into their luggage. Some people have listed things that I think people might already bring (suncreen, after sun lotion, chapstick, etc). If you have items like this then it makes more sense to give them out about a week before you leave.