Hi there,
That’s a really interesting idea. So, you could have a product in your store for people to purchase the membership. To do that, it might be easiest to use a membership app like Bold Memberships or AAA Membership. This would handle automatic tagging when someone becomes a member and removal if their membership lapses, as well as reminder emails. Otherwise, you would have to do all that manually.
Then, create a free shipping code for each year and have it be only applicable to people that are members. So you would tell new members that the free shipping code for 2018 is freeshipping2018 and then on Jan 1, that the free shipping code for 2019 is freeshipping2019. You can set up the discount so that it automatically and only applies to people who have memberships. So if someone’s membership lapses, they will not be able to use the free shipping discount.
You can read more about creating discount codes here.
Hope that helps.
Todd
ShopClerk Order Tracking for Shopify