I have been raising bees for three years - the first two winters I suffered complete losses. Each year I started with three hives - the first two years I started with packages of Italians, this past year I started with 3 nucs purchased from Merrimack Valley Apiaries. They were Carnolian hybrid bees. This past year I had the nucs in the hives on May 6th. One got to be so prolific I was able to pull off a split 2-1/2 months later. Each hive built strength and took on personalities of their own. Now being up to 4 hives I did everything in my power to make sure they made it through the northeast winter. Knock on wood - they are all still thriving with adequate numbers - even the small one that was the offspring (split) from the largest hive.
The only thing's that I did differently were, I purchased and installed nucs and did not start with packages. Next, I treated for mites in the early fall with Apiguard given that I had found evidence if mites. Also, I insulated the top of the hive above the inner cover and left them a top entrance (3/4 in. hole) in the front and back of the hive. Additionally, I fed honey balls beginning in February even though the hives were still heavy. The reason for this is that many of the bees were on top of the frames in the upper deep.
To summarize, I have not lost any hives / colonies this year however both of the last two years I had 100% loss @ 3 hives each year.
I am one happy beekeeping dude although I'd be a whole lot happier if the flowers would start to bloom and this snow storm was not dumping an inch of snow each hour for the next 14 hours!