I have now decided to increase the length of my ordinary weekday runs from 5½ to 6 km. (3,7 miles) I have measured the distans with my car and decided a new turnaround point on the bikepath. On my last run I tried it out and it felt good, I guess I could have been running a bit longer but to avoid injuries I will now stick to the 6 km distans for a while to see how I manage.
On my weekend daylight runs I will not measure the distans, I will keep on running the way I usually do, improvising the route, and run just for the joy of it. I usually don't decide where to run until I get there. I usually keep on for about 30 - 60 minutes, depending on the weather and how I feel. Afterwards I usually estimates the distance by looking at a map over the area.
I will also try to run on my lunchbreak some times, but then I will not measure the distance, but the time. I will set my watch alarm on 20 minutes, run a certain way until it beeps and then back again, with my ordinary speed that will be about 6 km, maybe a little more, maybe a little less. I don't find it necessary to count every km that I run, it is more important to just enjoy it.