Cart Abandon | "Date of Activity" Constraint

For the date of activity constraint, is there a trick, or a way to use SQL to have a custom time period?

Example use case: We're using a Marketo program and some Custom Data Objects to track "Cart Abandons" on our self-check out. A person would come into the program when they start the check out process, when the custom data object pushes in their purchase information, they would be marked as a success, and removed from the program. If they began check out, but didn't finish, we would like to, after 72 hours, send them a "Please complete your purchase" email. 

The way I would like this to happen is through a daily batch campaign:

•   Smart List:
  • Program Status was changed to "Member" at least 72 hours ago.
    and
  • Program Status was not changed to "Success"
• Flow
  • Send email

The date of activity fields listed are either hard dates or are inclusive of the time period, meaning it would take everyone in the last 72 hours. And there is the "in time frame" option, which is workable, but a little limited.

Is there a way to maybe use the {{system.dateTime}} token to capture the people who were changed more than X hours, days, months ago? 

Or, alternatively, if there is an easier way to go about this, I'm open to that as well. I had originally thought about using wait steps in the Smart Campaign that would capture them as a member, but as this is the first time we're setting something like this up, I'm nervous about the potential volume of people that will be in that Smart Campaign.