When it comes to running tired my opinion is that it's all about how you feel during the run and not before and after. My personal experience of running higher mileage has been of general and persistent tiredness that is alleviated by going for a run. I'm tired, but the run still feels good (at least most of the time). You're going to feel persistently tired running high mileage because, well, that's the point to a certain extent, your body is adapting. There is obviously such a thing as overtraining, but the sign of that in my experience, is not general tiredness but a continuing series of runs that feel bad and a drop of in how well I can run my quality workouts.