I went up on the roof today for the twice a year inspection. Took a tube of Dicor with me. I clean all slightly questionable spots with alcohol, and then apply the caulk. But, to my surprise, I found both roof vent covers broken. The one over the bed would have leaked if it had rained. I know the vent covers were fine this spring and I have no idea how they got broken. Maybe a low hanging branch.
Anyhow, I'm sure glad I went up there. Just wanted to urge everyone to inspect your roofs at least twice a year, you'll never know what you'll find.