Help me support that doubles and higher mileage are good?

At the end of the day it's your life man. Your the one putting in the work and time. You shouldn't have to prove anything to anyone. Make running be whatever you want it to be. Is running higher miles dangerous? works for some people and it doesn't for others. The thing is though you'll be putting in the work. No one can say you didn't try then. Best of luck bud.

You might be looking for scientific articles but from my experience the only useful way to figure out the right way to train is to look at what the top runners do. I have this view because I've found that most of the training information out there(especially books) is geared towards people who are not fully committed and are therefore looking for some secret way to work less. If you think the same way, I would recommend this site http://www.bunnhill.com/bobhodge/ There you can take a look at how people trained before everyone started looking for a shortcut.

The poster above is correct. Almost all running books and websites are going to be geared towards the casual runner.

Best way is to look at what the good and great runners did in the past. 90% of the time, it is going to be high mileage and doubles.

Also, check out this article. They looked a strength training, but the physiological/metabolical impact is the same across sports. This was in JAP too, highly ranked journal.