The reason they get addicted to ether is that ether explodes rather then burning. A lot of people think that a gas/air or diesel/air mixture explodes to
power an engine but in fact it needs to burn to produce any real
power. Over time the ether explosions will break the top compression ring(s) which only makes matters worse. Ether should always be your absolute last resort and even then only in very small doses, preferably introduced while the engine is already turning over. Spraying a huge gob into the intake and then hitting the key is just asking for trouble.
As others have already recommended, figure out some way to introduce even a little bit of heat. For cold starts the
batteries need to be in perfect condition. Warming the
batteries can also make a huge difference. Oil gets thicker as it gets colder creating extra drag which slows the cranking and makes the engine less likely to start. The oldtimers used to drain the oil, warm it on the
stove and dump it back in. That accomplished two things - it made the oil less viscous and helped warm the block. I have installed pencil heaters in the oil pan on diesel engines and it doesn't take much wattage to make a huge difference. I also run 0/30 or 0/40 synthetic oil in any diesel engine I expect to routinely start in cold
weather.
Heat soaking is a technique whereby you crank the engine for maybe 30 seconds and then let it sit for a couple of minutes before cranking it again. The theory is that the heat of compression will spread through the block. It takes good batteries and lots of reserve
battery power but it can be very effective if done a few times in succession.