Keeping it cool is as much about controling an outbreak as it is about preventing one. If you get a bettle or two they are likely to much on a few cigars in one small area of your humidor and lay thousands of eggs in those cigars. If those eggs don't hatch, and you throw out, freeze or smoke that area, you are good. On the other hand if you don't notice the couple of bettles until their thousands of eggs hatch you can loose hundreds of sticks. Even if only a few eggs hatch at that temperature instead of thousands, it's a huge diffirence.
Don't remember the exact life cycle of these things, but you can be into the third generation before you catch it, if you are not in that humidor every month.