I really liked your idea and thought it would be helpful to have a native option in Target to do this because of that I have submitted this feature request here: Time on URL Target Audience please help it get more traction by:
1. Voting it up.
2. Adding your own personal comments on why this would be helpful.
Thank you and hope this helps!
Mihnea Docea | Technical Support Rep, Customer Care | Customer & Employee Experience | Adobe | (:: 1 (800) 497-0335