We have Comcast at home, I put a UPS on the modem and router to keep it up for around 8 hours in a power outage, but the first extended outage we had I discovered Comcast's own backups only last 45 minutes here. So that made the UPS and a VoIP line as a backup pointless. I however keep the VoIP lines around for my old phones and because I'm using some really cheap providers, with my own equipment, so it works out to be less than $10 a month.
If shit hits the fan then Verizon will have to do, if they somehow fail (like they did in FL during their last hurricane) I have extra SIM cards for other carriers laying around that I can activate in a pinch.
Also, I rewired all the phone wiring in the house with Cat5 back in 2011, and gradually ran cat5 for ethernet. Every room has a phone jack (was like that when the house was built), but the original wiring was a nasty mess that resulted in many reliability issues with the phone, and DSL when we had that. I have everything terminating to 110 blocks, and the jacks are the keystone type with 110 punchdowns as well. Makes for a solid connection.