So to answer the questions... I purchased the unit as a runner with all filters supposedly replaced. $1200 - a little steep from what I've read here, but it came from a reputable army surplus store that sells "pretty" 002a units all day long for $1800-2200. Mine's an ugly as sin brush painted green with a mismatched tan output box and some dents that probably occurred when other stuff that wasn't really needed got shoved in to it. Paint transfer kinda confirms this. I topped off the fuel tank on the way home (mistake 1) and ran it for two hours with a 1500 watt load (mistake 2) before I did anything else. After the two hour run I took the fuel strainer out to figure out why my fuel gauge didn't work. I don't think I've ever seen that much crud inside a fuel tank. Verified with a local farmer I had a pretty bad algae problem in that little tank - was told I'm pretty lucky I didn't plug everything completely shut.
So here's what I did: Pulled the tank and cleaned it thoroughly. Cleaned it again. Pulled the dip tubes and the fuel gauge and cleaned one more time. Pulled and checked all of the filters. replaced one fuel pump filter, everything else somehow managed to stay near spotless but I replaced the first fuel filter anyway. Cleaned everything else. Oil wasn't bad but looked like it had a little time on it, so I changed oil and replaced oil filter. Checked air filter. Checked preheat and glow plugs with multimeter - all good. Fixed 10k box so that it properly indicates percentage of 5k load, and no there wasn't enough wire in my box - I had to add about 20" to each wire. Turned reconnection switch to check functionality (mistake 3) then spent two hours loosening the nuts on the switch while still mounted in the output box to get it back to 120/240 single phase. Considered removing handle, probably will soon. Replaced dodgy herz gauge with a digital gauge that shows Hz and voltage. It's officially awesome to be able to see those numbers from 30' away. Made a cart for it out of 4x6 ash, extended exhaust to go just outside my barn with unit inside (yes I have a death wish) and made a nice heavy #8 suicide cord. Manual transfer switch and associated wiring is going in next month.
How prepared am I to run extended? Sorta kinda prepared. All three fuel pumps work on my unit, and I've already identified which hoses need to be swapped if one or both of the primaries fail. So while I don't have an official spare pump, I'm comfortable with what I have for now. When we lose power it's typically less than 12 hours, so I'm not too worried about filters. That said, I'm adding spare fuel filters, oil filter and glow plugs to my "need" list. If a fuel pump filter clogs I can steal off the auxiliary, and I'm not too worried about the air filter with the unit being inside. I suppose mice could create mischief and make for a bad day, but so far (fingers crossed) it hasn't happened with anything else.
Fuel stores - I have about 5/8 of a tank per the gauge plus a full 5 gallon can, so 12-15 hours run time if mine consumes the typical half gallon plus per hour. I have a list of the closest stations that sell diesel (pretty common in farm country) plus a friend with a bulk tank if things get bad. I'm a little lax on fuel stores because of my location - I'm the last house on the line serviced by Detroit Edison, with lines coming in from the east. West is Consumers Energy. Only once in 17 years have we had a severe enough outage that both companies were out in my neighborhood, so fuel is almost always 5 miles away in either direction.
Fuel storage - plastic cans (except the gennie itself) with known good seals. Fuel was treated with cetane boost/stabilizer and a double hit of biocide when it went in to the can. Fuel in gennie got same treatment. I verified when I bought in March that station was still on winter blend, so gelling shouldn't be an issue. I don't have any other diesel equipment, but father in law has a diesel mower and compact tractor. I'm planning to store fuel no more than a year and give whatever's left to him. Stabilizer bottle says fuel is good up to 2 years treated, and I've read on more than one forum it's more like 5 if it stays sealed so unless you tell me different I'm not too worried. As for running every month, I've been doing that mainly for two reasons - 1: to flush any critters hiding in the lines out and 2: to burn off a little fuel. I could easily switch to twice a year as that's about all my gasser saw, but I don't want to inadvertently store fuel for an eternity either.
On the subject of overthought, if the genset DOES fail I still have my 6500 watt gas unit. It's a tinker toy compared to the MEP, but it served it's purpose for 16 years. It still runs, but my fancy new high efficiency furnace really wants 60hz and minimum 115 volts or the onboard controller gets grumpy. Even after a carb rebuild and valve adjustment the old gasser just can't keep tight enough control on the settings to keep the furnace happy. The 002 is dialed in to 122 volts and 61 hertz. I don't touch it. Startup is 60.4 to 60.6 hertz, and after about 5 minutes we're humming along at 61. At 120% load (six space heaters at medium - 900 watts) the 002 drops to 121 volts and 59.8 hertz - scary how well something works when it's overbuilt for Uncle Sam. If I DO need the gasser I have an occasional use wood stove and probably a month's worth of firewood, so in theory we could heat with wood and run everything else off the little guy. I don't have a sump pump to worry about, so 12 hours of fuel could easily get me a couple days if I ran a couple lights off the RV batteries and inverter and just ran the gennie when it became necessity.
So... how'd I do?