set up triggers for items Any way to set up triggers for items in their cart  to remind buyer to check them out after 30 days?
Yep:

Commerce Abandoned Cart Notification


  This module allows you to notify your customers by email about their abandoned their cart.


It's in dev so be warned; I'm not aware of any other pre-existing solutions, but writing your own module for this would also be a pretty straightforward option if that module doesn't work for your needs.