Like Archie, my run-focused weeks only has 2-3 running sessions (1 long run at jog pace and 1-2 short runs (2-3miles) either easy or with sprints/hills) with 1-2 biking sessions and 1-2 swimming sessions to rest/build up other muscle groups. For me, I did run/walk intervals from couch to 5K then after I could consistently run 5K (about 35min for me) I started adding 1/2 miles (about 5-6min) to my long runs every other week until I reached 60min (5-5.5 miles for me).
Psychologically, during those long runs, particularly at the end, I keep telling myself, "You've been running for XXmin already, what's another 5 minutes? You haven't come all this way to quit and have to start over." It helps to be outside because "If you can see it you can run it." so I can get distracted just running to mail boxes or signs for that extra distance.
