If all you do is “not more than 4.5 hours per week or 30 miles per week,” it would get incredibly boring and you’d quickly plateau. Eventually you’d stop seeing gains and probably get tired of running and quit altogether.
Instead, I think it’s helpful to view training as cycles, building up at some points and ramping down at others. Even elite runners never “overdo” it all the time— rather a bulk of their miles are recovery or “junk” miles. They save the most intense training for just before tapering to peak in competition.
Not all miles are created equal. One mile of speed training is not the same as a five mile jog. Stress and rest are equally important. Push your body, and listen to your body.
Trying to stick to a one-size-fits-all formula is a recipe for burnout, boredom or both.