Formulated by Barney in First Time In New York, detailing how relationships are like freeways, and there are exits that can be taken to get out of them: 1. * 6 hours (aka one night stand) 2. * 4 days 3. * 3 weeks 4. * 7 months 5. * 1.5 years/18 months 6. * 18 years 7. * death