I have not used cedar hive bodies,
but the past 2 years I have used cedar shavings (used for dog bedding)
under and around my hives in hopes of hindering the pupating of Small hive beetle larvae.
My bees are still in the hives and I 'm not sure it's doing much hindering of the larvae.
I bought cedar bottom boards and still have bees and mites. Around here I get several swarm calls a year from bees that hang on cedar trees to rest. No negative or positive differences noted to my other hives.
I dont have any cedar hive bodies but I did cut a bee tree several years ago that was in a hollow cedar tree and they were doing just fine. From the color of the comb I would say they had been in there three or four years.
Cedar is great for lasting a long time and repelling insects that consume or bore into wood. There are two different kinds of cedar, aromatic cedar and normal cedar. Apart from insects that eat or bore into wood normal cedar does not seem to have any other effect for the hive... apart from being a lightweight long-lasting product that is water resistant on it's own. Since it isn't prone to rot, cedar hive bodies should last at least twice as long as standard white or yellow pine (Hence the reason that decks are often made from Cedar).
Beware of aromatic cedar however. Although it might keep the moths away, it might also drive the bees away. A person that wanted to test the effects of this could get those cedar closet hangers and place some above the inside cover and/or below a screened bottom board to test it's effect on the bees (cedar hangers are almost always made with aromatic cedar to keep moths away from your clothes).
Aromatic cedar is very expensive however, so if you're finding cheap cedar somewhere, odds are it's not aromatic. I want to say that aromatic cedar only grows in the western US, but for the life of me I can't honestly remember which one grows on which side of the country, so don't take my word on that one.
I have alot of cedar trees on my property and was also wondering if they could be turned into hives. Has anyone here ever cut their own cedar to use this way, or has the wood been store bought? The hives I have are standard hives and they have cedar bottoms. I assumed they were made with this kind of wood because of the location close to the ground and it's durability against the elements.