I don't think I'd do very much to prepare for that scenario.
You might plan on riding out a storm, thinking utilities might be out a day or two max. Day 5, still no utilities, no known date for resumption of services, and supplies are running extremely low. How do you get out?
If you forecast that your supplies will be very slim on day 5, and you haven't left for greener pastures by day 3 or 4, then the the worst case is already unfolding. GTFO before the worst-case ever happens.
But in that worst case: One can call on someone else for help. This is one of those situations where it's time to cash in some favors, and/or where it pays off to always be friendly and helpful with to the neighbors even if they really seem like a bunch of assholes. (The time to start being friendly with the neighbors is right now, by the way.)
(My own backup plan only keeps me rolling both semi-comfortably and independently for about 24 or 48 hours without power in the winter, so I'm leaving after the first night or ASAP. I don't have the complications and niceties offered by something like an F-150 Lightning, but finite resources remain finite no matter their form.)
I admit it's less efficient to have 2 energy stores, but given we're already discussing potentially life threatening situations, I'm not really looking to optimize for anything except having as many resources as feasible on hand.
Money is limited, so sharing resources between situations lets you be prepared for more situations.