Winter: wondering how the bees are doing

I am sure its the same for all beekeepers in winter time; on nice sunny mild days you go and have a quick look at the outside of the hives.  You are happy to see that they are still standing and there is no apparent external damage but it feels very spooky that there is no sign of activity.  You know that its only 6 degrees so you should not expect the bees to be flying but you can't help wondering if they really are alive and happily hunkered down or ....your worst fear... have they perished. We now have 4 hives to worry about; last week in the sun one hive had a few bees coming and going. Seeing this made me wonder why the other hives had no signs of life.  Its been freezing every day since so there has been no chance to open them up and check. But even on a nice day, will it be right to check on them just because I am anxious?  I will try and keep my nerve until after xmas and then find a day to open up and do a full check, add any fondant and douse them with varroa treatment.   Till then I just have to live with this nagging doubt.  Its weird to feel like this as I am not, by nature, a worrier and never feel like this about my kids.  Its the prolonged not knowing.......