We go 4 weeks tomorrow and I've started putting toiletries, suncream, passports, dollars, first aid kit, etc into a holdall so I know where they are!
Won't put the clothes in until the weekend before though. It's difficult for us this time as we're off to cornwall and eden project for 4 nights, 2 weeks today, so we'll need some of our clothes for that - though probably not as many tshirts and shorts as I hoped with this weather!!!