I don't know about "5%"...but yes, I've used it on any trip in hurricane season.
Be careful about the grades available. e.g. Access America sells a couple different level at different premium costs. The one I bought unfortunately only kicked in with benefits if you lost > 48 hrs of your vacation time, so when our first attempt to land in Belize City occurred in the middle of a tropical storm, and the plane turned around and landed back at DFW instead (that was a looong day), we got nada.
I think the premium ends up being semi-related to how soon you buy ahead, but I haven't tested that. .e.g. if you buy way early they're insuring against a longer period of time before the event can go off successfully, since one of the things being insured is that YOU don't get injured in a way you're unable to take the trip....then again, you might also think they'd crank the premium right at the end to prevent buying when you already have a strong inkling (e.g. searching on www.hurricane.gov!) that a trip is about to go south on you
Might make an interesting study testing out their online quoting with different dates to see how it influences their pricing....