I know they are for winter and summer, some people say take them out for summer when hive gets busy what do the veteran bee keepers say?
Take'em out, unless you have a really weak hive that needs protection from robbers. Otherwise a reducer will slow down the foragers' comings and goings, similar to the way a queen excluder slows the girls down. Also cuts down the air flow in summer when you need ventilation to keep the hive from overheating when the mercury around here tops 100 degrees.
You might want to add your location to your profile. Helps as sometimes advice is area specific.
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I estimate he need from number of ventilating bees.
When Ihave hives on canola field, I keep the entrance widely open.
When I open totally the entrance, the lower box will be cooler and the queen moves to lay in upper boxes.