One if not the key to growing succulents in cold climates is controlling the water. Keep them dry and most will cope with much lower temperatures. The interesting bit is how far you can push this; there is a big difference between a few hours of cold followed by a day of sun and days or weeks of never getting above freezing. So controlling water is a bit of a no-brainer.
The traditional view is that you stop watering plants in greenhouses at some point before the first freeze and start again once everything has warmed up. It is amazing how strongly this view is held or just taken for granted. Last spring I went to visit an echeveria nursery and the owner had the most amazing collection of plants. He was in the no water camp, not so much out of strength of feeling, but because this was the "official line". As we looked around he told me how he never had any luck with certain plants. We went through those he struggles with and they were all plants that liked more water to grow. It had never occurred to him that not all echeverias will cope with no water for 4 - 5 months. I suggested that if he didn't want to water all the plants, it may be worth setting part of one greenhouses aside for plants that needed some water. Next time I visit I will find out if he did and if this solved the problem.
For me though it is not just about keeping plants alive. It is at this point in winter, after a couple of months of no water, that the plants are starting to show the effects; leaves have lost their plumpness and are saggy and often cracked. Older leaves may have died altogether. The echeveria pink frills below is a sad sight compared to normal:
As is this agave, you can see that the lower leaves have started to crack.
So at around this time I wait until we have some sunny weather forecast and give them a little water. I do mean a little water, there is obviously a fine line between giving them a little drink and getting them back into growth. I have learnt to my cost that too much water and you get leggy growth. In my experience this top up not only helps to keep the plants looking a little better over winter but also means they are in better condition to get going in spring.
I have no doubt that some people will be horrified that I water my succulents over winter, but for me there are very few rules in gardening that work uniformly and I prefer to take my experience of growing each plant throughout the year to guide my treatment. Most of the time it works, although some times I am wrong. Thankfully I keep records of the failures as well as the successes and this guides the treatment for future years.