Chopin I like it, we do run run.......
I'm another one who's enjoying the idea of additional benefits from the running, strengthening bones, being outdoors etc. For some reason, before this, I was struggling to get outside, almost felt agoraphobic, I'd find any excuse not to be out there. Now I just go.
On the inner chimp, I read somewhere, can't remember where, that our bodies are much less tired than our brain tells us and if we ignore the brain message of being tired, our bodies are capable of keeping going beyond what we believed (caveat with current news stories, not extreme sports or activities), but for running 30-40 minutes, tiredness isn't a reliable indicator provided you're otherwise healthy.