I've got about 3" extensions on a few of my hives and the bees hang out there but I wouldn't say there's any benefit to them other than making it possible for me to observe them sitting there- the bees hang out on the other regular 2" entrances as well and I've got one hive with no landing area at all and the bees just hang out on the front of the hive.
If you're hives are on or near the ground, an extended landing board might be helpful to keep them off the ground- mine are on 6" tall platforms I won't bother with extended landing boards in the future.
George-