As I build up the fitness, I start to set lower levels on my training. I was thinking about this during my 6 mile run just now. When I first pick back up after a month or two if I happen to take that long away, I generally use a 30 minute run as a baseline starting point. This is not to say you should or to judge people starting with less or more. It just fits.
Now that I have a stronger base, I look at the 45 minute run or the 5 miler as my base easy run. Today, I ran a 6 mile run in about 51:00. It felt good, fluid. Some of the great podcasts from AthleteonFire have really been keeping me in the zone focused.
The reason I mention the length of base runs and what not is that as you may begin to build a base, progress with your run timing and routes. Changing up run pace, length, etc. is beneficial to your mindset, your body, and your motivational levels.