Interesting take on standby generators. Ours is ~5.5 years old now: it's a 20KW Briggs & Stratton (both generator and engine branding) running on a 500 gal. propane tank, with a dual 200 amp split transfer switch (that's the thing that detects power loss from the street, starts the generator, and then flips over the power). It has worked well for the time we've had it, although it wasn't installed yet during our 2 most challenging outages in 2012 (5 days and 2 days). The failure on Dec. 23rd was apparently 100% my fault, since I last changed the oil in Dec. 2020. I guess it had consumed enough oil in 2 years to take it just below the "low oil" point. I don't really have any reference points, as I've never owned a non-portable generator before, and I'm not trying to say "mine's the best", but I'm certainly happy with it so far.I normally stay in my lane with the small boat crew. I'll add my two cents on this one.
The best way I know to maintain a battery is by "floating" it with a regulated source. In my case, being a HAM, I use a regulated analog power supply. The supply powers several things but the voltage at the battery is kept a 13VDC. The battery is used for marine use and will be fast charged, or "equalized", from time to time. I retire in a month, so I'll do this more often.
I work in TV broadcasting and also do the day-to-day upkeep on large generators. 3 diesel and one natural gas. Having done this for many years, I have learned that dedicated generators are a maintenance pit. As some of you have said, whole house generators will fail when they are needed most. Here in my part of the country, that storm that gets the power will also surge the automatic start circuits. I will never have a generator in standby at my home. I have a 5K and will upsize when the time comes but it will be portable.
(The main reason for the generator was having aging parents move into an in-law apartment. They really can't handle uncertainty, with our well water on an electric pump.)