You should give yourself at least six (6) weeks to prepare for your campaign prior to launch. You will need sufficient time to strategically plan your crowdfund including creating a short pitch video, designing your campaign page, building up your network, and pre-selling your rewards to supporters who will back your campaign within the first 24-48 hours.
Filling out your campaign page can take anywhere from 1 hour - 3 weeks depending on how much time you want to dedicate to it!