I don't use them. I don't see any use for them.
Yuo use lower entrance either. Do you mimic nature way ?
I look your homesides and you have landingboards there. :P
I see a lot of use to landingboard. It is just nice for many reasons. At spring when it is cold I put larger landingboard. When bees come home they should get in quickly. On rape field when bees come with heavy load they drop to grass. There are hunders of bees resting in front of hive when they tried to fly into hive. Last summer I had good pastures and bees need to fly only few hundreds meters to home. They flyed direct into hive.
Lower entrance is very good because it keeps hive warm. Warm air goes upp. In our climate warm is very important. We have just few days over 25C during summer.
But in Finland many are such opinion that landingboadr is vain. As you see, it is same what you use.