David Letterman , who 's retiring in 2015 , has been a talk show host for 33 years . David Bianculli says it 's more than Fallon 's `` Tonight Show '' turn . He says many people see late-night shows as short bits or viral videos online the next day . Fallon , of course , is superb at this game ; his musical bits alone are guaranteed to feed a steady course of streaming videos . The other big change is that there are now two major networks and they have different rules about what can air on their schedules at any given time. Internet age has devalued Letterman 's forte of monologue , hourlong show .
David Letterman , who 's retiring in 2015 , has been a talk show host for 33 years . David Bianculli says it 's more than Fallon 's `` Tonight Show '' turn . He says many people see late-night shows as short bits or viral videos online the next day . The other big change is that there are now two major networks and they have different rules about what can air on their schedules at any given time. Internet age has devalued Letterman 's forte of monologue , hourlong show .