Have you read the research of Anders Ericsson? He's the guy who researched the mythical "10,000 hour rule."

In his research, he makes the distinction between "purposeful/deliberate practice", where you are actively training a skill, and "naive practice", where you are just doing what you know how to do.

Purposeful practice is the best way to improve, but it's also exhausting. If you're doing it right, you can really only do four hours of purposeful practice (or similar intensity of work) a day before you hit mental fatigue. (Note this four hours is free of distractions and multitasking)

So that's how I schedule my hobbies. I set aside four hours for intensive work without any distractions. After four hours, I can feel the mental fatigue set it, and I let myself spend the rest of my time on non-mentally intesnive hobbies. (Unfortunately, on days where I work, I reach mental fatigue by the time I'm home)

I'm trying to reduce how much time I spend reading and being on the internet...What sort of split do you guys have between your hobbies which are better for you and things like watching tv, internet, etc?

I think the split between "better for you" and "not good for you" is a little misleading. The real split is between things that cause fatigue and things that don't. It's possible to minimize the time you spend on media in a more constructive way when you consider this.

When I reach mental fatigue, I try to switch to hobbies that cause physical fatigue, but not mental fatigue. A brisk walk is physically fatiguing, but helps restore my focus. The same thing goes for household chores -- they're mindless enough for me to do post mental fatigue.