How long does Mobil1 last if not used, but installed...

Do not cheap out on the oil ever.
Change it

How long you leave gas in there?

No sense throwing money down the drain. When does the unit recommend changing it? I'd go by that.

Gas is double treated with stabil and lasts at least 2 years. I've run it 2 years old and it runs great. I don't let it get older than that before I pull it out and put it in the car and put newer stabil treated gas.

I'm on the fence here. How long does oil sit in a container before it is installed? I hate to change out oil that seems perfectly fine, but I don't want to risk anything either...

I change my oil about every 20 hours or so. It's the lifeblood of your car engine and of your generator engine. Don't cheap out, I agree. I also take care of my boat engine the same way, and I change the oil in my vehicles every 3,000 - whether they need it or not!

It's doing just fine sitting in your sealed crankcase. 100 hours of run time or 4 years, which ever comes first, if you ask me

Instead of guessing, call Mobil 1 at 1-800-275-6624 tomorrow. That should give you one of their product engineers.

You might post their answer,

Bill

How often do you think they change oil in a fire engine or ambulance?

Me - I change the oil and clean out the air filter etc... once a year
Sometimes with less than 15 hours on the genset other times with 50 or more
Wally World has Mobile 1 - a great oil and a good price

I wonder what the Yammy owner's manual says about long term storage...?