[Quiet Man Cometh]

That's another one I judge by feel rather than by what I know about grammar. The main thing is to remember that a run-on sentence and a long sentence are not the same thing.

Back to the clause thing. Google describes a run-on sentence as what happens when two independent clauses (complete sentences) are attached in a strange way. Here's the example they use:

"I love to write papers I would write one every day if I had the time."

"I love to write papers" would be it's own thought, and "I would write one every day" is another. The problem here is that they aren't made distinct from each other. They are stuck together as though they are the same thought, even though the topic changes from how much the person likes writing to when they would do it. You could fix this example by using "and" or by making it two sentences.

"I love to write papers and I would write one every day if I had the time."

"I love to write papers. I would write one every day if I had the time."

The sentence you wrote up there looks alright. I'd say the best way to avoid run-ons is simply, when in doubt, make it two sentences.