Several hives of mine have become accustomed to coming and going via the upper
vent I used this winter (nothing more than a half-round opening in the top
board).  They are completely ignoring the traditional now-fully-opened opening
at the bottom of the hive.  Am I worried about this?  In each one of these
hives, the queen and most of the bees seem to be in the upper of the two deep
boxes.  Thanks a lot for any opinions.
JRH