I'll be putting a 10,000 watt unit into my country home, wired into the main electrical panel, so have thought about this issue (now use a portable, gas-powered Honda in my city home).
The better units cycle on for 15 minutes every month or so, and carb gelling of fuel shouldn't be an issue with diesel or gas. However, fuel will deteriorate (gas much quicker than diesel, but both will even with a fuel conditioner). The point that won me over was fuel capacity and run time. After Hugo (Charleston, SC) in 1989, I didn't have regular power for 7 days, and many folks for longer (in rural areas, many weeks in some cases). I'll have a large propane tank for the country house (water heater, dryer, stove), and I've calculated that if I fill up the propane tank a few days before a hurricane might hit, I'd have, if necessary, hot water, food, dry clothes and power (propane powered generator) for up to 10 straight days. I could keep equivalent amount of diesel around, but then I'd have to have 2 tanks (diesel and propane), and keeping diesel fresh in a large tank, for a guy with only a tractor that uses diesel, just isn't practical. So, a propane powered generator, and a large tank - very low maintenance (clean carb and plug) and emissions, & usable for other stuff (dryer, oven, water heater, barbecue).