When should the documents be sent out for the 12 Day Detox

If you use the 12 day detox as an individual program and mail the contents to the client as soon as they sign up using an auto-responder, when would you start to send the daily emails? Would you suggest somehow asking them when they want to start the detox–like have them email you with a start date they select?
Send the first email when they purchase and sign up.  Send the rest of the emails daily.

You want to set the start date for when you are most available to participate.