I live at the level of Anchorage. You live some hundreds miles to north? I depends what is your local climate.
In our country 64 degree -30C (-22F) temperatures in winter are normal. The cold is not so bad as the length of cold period.
And do not believe sayings " cold does not kill hives, it is moisture". In north both kills.
According to the weather service, on average Anchorage has 3 days per year where the max temperature is <= -20 F and none where it's <= -40F. Fairbanks, on average, has 44 days where the max temp is <= -20F and 10 days where it's <= -40F. Also, on average, we have 221 days (7 months) where the temperature doesn't break 32F. Those are averages, though, and the variation around that average is considerable. I'm a bit of a weather watcher, and according to my records from 20 years of living here, we've never seen a winter with less than 7 days below -40, and we've seen eight winters with more than 30 days below -40. We've also seen a four years with 10 or more days below -50. So, as you say, the length of cold period is a significant factor. We also have an extremely dry climate here, so moisture is likely not as big a problem here as in some places. Lots of things can survive a severe cold snap. An extended cold period with extremely low humidity is another story. Things freeze dry.
First of all insulated hive bodies are very useful. If you have solid one inch wall in deeps, it consumes 50% more food.
I've assumed that was important, and I've worked out several ways to insulate my TBH hives. The ones I tried (unsuccessfully) to winter in this year were built from 3" styrene board, with just a couple openings for ventilation. Those were a bit clumsy and not so sturdy, so I'm building some insulated overpacks to try next winter.
The size of wintering hive depends how much you have brood in August. I put hive in one deep for winter if it is possible. If August has bad weathers winter will be smaller and hive must be in one deep over winter.
OK, my hives are 90 liters volume, which is a bit more than two deeps. However I can reduce the volume with a follower board to any size I want. So, if I have a small colony going into winter, I can move them all to one end and reduce them down to about 1 deep, but if I have lots of brood going into winter I might give them the whole hive. That makes sense.
I prefer big hives, not for over wintering but for early yield and for good spring build up. That is why I use now electric heating in spring.
I've considered trying electric heaters. I've put automotive oil pan heaters under a metal sheet in the nesting shelves for my pigeon loft and plugged it into a thermostatic cord and a timer so it only comes on for a couple hours at a time and only if it's below -10. I have squabs surviving year-round that way. Seems like something similar could work with bees. At what point in the spring do you begin using the heat?
I take all honey away. Perhaps 10 pound will be in brood frames when I start feeding. There is no advantage to leave honey for winter.
So do you feed them lots of syrup in the fall and let them store it to use, or do you have some system to feed through the winter?
In spring is a big advantage if you put 2-box colony into one box and take extra room away. Spring build up will be faster.
Again, this is something I can easily do with a follower board in my TBH's.
If you keep hives in shelter over snow time, hives will do fine even at the level of 65 North.
This is something I've considered, but haven't tried. The only people around her who do overwinter take a couple hives into thier basements. Several years ago a local fellow got a grant to build a bee wintering house. He was able to overwinter some bees, but said there was no way it could ever be economically feasible, and no one has tried it since as far as I know. I have lots of excess hay bales that aren't suitable for feed, and may try building a hay and pole shelter to put some hives in next winter.
The most important is that you have a stock which survive well at you level. It may be Italian or Carniola. If you bye every year queens from south, they often have sences to adapt your year's running. They make brood too late and get nosema and are restless in winter.
I bought bees from Keith Malone in Anchorage last year. He sends his queens from colonies that overwintered there down to California to a guy who produces packages with them to ship back up. As I said, Anchorage is not the same as the Interior of Alaska, but I don't know any way I can get closer to genetics that have overwintered here. I'm pretty sure I can't legally get bees from Canada right now. I don't know if I could bring in queens from Finland or not, but I'm not ready to risk that kind of investment yet anyway. :-D
TBH is very demanding at these levels. There is no advantage in this method. It is mere a toy. But it depends why you keep bees.
If you like to keep bees as naturally as possible, that is a false because on these levels there are no honeybees. For bees these are edges of survival and it is vain to play Africa.
You may well be right, but I'm hard headed enough that I'm going to give it a hard try anyway. I worked for a guy with 500 langs when I was in high school in the 1970's, so I know how they work, and I know any type of hive can be managed lots of different ways. I don't expect I can run a TBH in the Arctic the same way they do in Africa. On the other hand, I'm not a highly experienced beekeeper, and I may well be setting myself up to fail. If so, I'm doing it with my eyes open.
Also, this is the edge of the survival limit for everything on my farm. Angora goats and cattle can't survive on their own here. I'm at the northern limit of where wild pigeons are found. Chickens are tropical birds. Ducks and geese leave for the winter. My garden is not natural here. The hay we grow is not native this far north. Many of the trees we grow are not native at this latitude. I don't do any of those things natually, because they're not natural here. However I do use lower-technology, less resource intensive (and often more labor intensive), and often unconventional methods compared to producers in other areas. Commercial producers in those things have told me there's no way I can succeed in a harsh climate if I don't use the latest technology available. I (and others) have proven them wrong. I don't see why bees must be the exception to that.
The summer is too short to start every spring a new hive. I ahve noticed that in Alaska you have southern methods in beekeeping because it is so easy to get new bees for summer.
You're right, and that's why I'm looking for information on this forum. People locally make some very strong arguments that killing bees in the fall and buying packages in the spring is the only rational choice. I don't buy it, so they all just think I'm irrational.
You may take bees from those who kill hives. Over winter them and sell them back in spring in good condition.
Now that's a great idea!
Thank you for all the advice!