Re: Is it common for a queen to switch hives?
I've had it happen 2 or 3 times to me over the years.
I think queens fly more times and for a longer period of time than some people think. I think they fly multiple days for mating flights. I've seen evidence of queens flying or at least leaving the hive in some fashion for up to 30 days after egg laying has started from a fresh new queen.
I would suggest combining your hives into one hive.
20+ years, raise my own queens, feed when needed. I treat, but have not perfected varroa management yet.