A recent study by Time magazine points to the long-term benefits of an active sex life, including a stronger immune system, less chance of depression and perhaps even increased longevity. Modern medicine is pushing the limits like never before. 48 Hours Investigates examines the latest developments on the landscape: new prescription nasal sprays, pills and creams to help men in the bedroom; older women dating younger men; a senior citizen's sexual journey; tips on how to put sex back into a sex-starved marriage. Correspondent Bill Lagattuta reports from the front of the ongoing battle against erectile dysfunction. The latest "weapons" include a newly approved prescription pill called Cialis, playfully known as "the weekender" because it can be effective for up to 36 hours. Another pill, called Levitra, on the market for only a few months, is already competing with the erectile dysfunction champ, Viagra.