Wife wants me to start brewing Lambics, like a monk, and also, some Sour Beers.
We tasted some sours in CA that took a few years to make, and it was DELICIOUS!
Thank for asking the question. My son is also considering this exercise. Some good links and comments here.
It might be wise to spec up for a few days beyond the most likely outage (??) or risk the on-going vocal displeasure of the consumer, in this case your wife. IMO that almost certainly would exceed 1-3 days.
In a SHTF situation fuel will be a substantial (perhaps non-cash) major cost even if it is available. The analysis might start with how much fuel you can reasonably store on your property and spec from there.