I've been using my 125 for a snowplow for almost 20 years. I keep it in an unheated shed. I use 10-30 synthetic oil in the crankcase year-round (along with some zinc additive) and I change it every year or two. I use HyTran Ultra in the Hydro, which I change out religiously, along with the filter, every 6 or 8 years, if I remember to.
I put a new battery in it when it needs one, which is about every 3-4 years, but I do not keep a battery maintainer on it. I have battery booster/charger I can put on it if it needs it, but I can't remember that last time it was needed. I use regular 10% ethanol gas, but I treat every can with Sta-Bil and Lucas Safeguard for ethanol when it gets filled. I date and rotate my gas cans so a can doesn't get forgotten and end up having 10 year old gas in it, however most of the gas I use is a year or so old for both winter plowing and summer mowing. I don't live on the tundra, but it does get into single digits most January's.
I actually put a new plug and points in it last year. The first set since I rebuilt the engine almost 20 years ago.
I have never gone out to start plowing and have the 125 refuse to start. Unheated shed. No block heater, no torpedo heater. It does require a bit more choke in cold weather and the hydro is a bit sluggish for the first few minutes.
I hope I haven't just jinxed myself.
What I am trying to say is that, in my experience, these things don't need a great deal of pampering to get them to run in any weather, just a little basic maintenance now and then and clean gas.