If you are willing to try a different SIP provider, try Nexvortex. We've been using them for about a year and a half, and they have been amazing. To be honest, we have had three outages with them.
The first was about 10 minutes, and they warned us a few minutes ahead of time (one of their carriers was having an issue).
The second was nearly 4 hours. During the big ice storm, their local LEC lost power after their generators ran out of fuel, but I have been assured that situation has been addressed.
The third time was a little less than 15 minutes, and I don't remember what caused that one.
Considering all the issues we had with Bandwidth.com before switching, I consider these folks phenomenal.
If you call, ask for Mike Nowak, and let him know John Wells sent you.