Renewal reminder - Smart List Logic
We want to send 7 / 30 day renewal reminder emails through Marketo and have built and successfully tested the emails using Velocity but I’m having trouble building the smart lists. (We thought this would be the easy part).
Our customers may have multiple products that expire on different days, as I see it from different discussions, there are 2 accepted methods of building a list for a renewal email. Using the 7 day example, they are as follows:
Method 1: (In future 7 days) and (in future after 6 days)

Method 2: In future 7 days but not in future 6 day list.

Method 1 fails when a customer has 2 (or more) products, one expires in 5 days and one expires in 9 days the customer makes the list even though they don’t have a product expiring on the 7th day.
Method 2 fails when a customer has a product expiring on the 7th day but also has another product expiring in the next 6 days. This customer doesn’t make the list because they are a member of the 'future 06 day' list that we exclude.
Has anyone come across simiilar situations or can anyone suggest a Marketo based solution to this problem?
Alternatively, if has anyone implemented a CRM based solution e.g. creating a 7 day / 30 day flag on the Salesforce object, I'd love to hear about that.