In reality, it varies depending on how extensive that list is. If your list is relatively short, it won't take you as long to make out the initial information. If you actively work toward building that list, it's best to include new names on the list at the end of each day based on customer sales or interactions with other people. That way, you can build it as you go. The truth of the matter is that most people never really stop building their list. It's an ongoing process, especially if you're building something for business or you're working toward getting sponsorships for an organization.