Having the ability to configure and adjust your beehive entrances can benefit both the bees and the beekeeper throughout the beekeeping season. Often times, you will need to adjust your approach during different times of the year, and having the ability to adjust your entrances and remain flexible over the course of the season can be very helpful.
For example, in a summer dearth when robbing activity is more common, the ability to reduce the size of the entrances provides assistance to your colonies when it comes to defending their hive against other bees. On the other hand, if you are treating for Varroa mites, these treatments will sometimes call for maximum hive ventilation, so having the ability to easily increase ventilation (via your entrances) will help in this regard.
Over the winter, your entrance configuration is very much a personal choice and will depend on your equipment (well insulated or not at all), as well as location (north or south), and your region’s winter climate.