Bushmaster has a suggested test to run after reassembling their AR. Confirm that the gun is unloaded. Cock it, put it on safe, and attempt to dry fire it. It shouldn't fire. Then take the safety off and dry fire it. It should dry fire. Finally, pull the trigger back, cock the action, and release the trigger. It should go forward a small amount with a noticeable click.
Apparently, this amount of dry firing is not a problem.
I have seen warnings against dry firing with the lower disconnected from the upper, as the hammer slams forward against the stop, which is not good for it.
After performing the above, I leave mine uncocked for storage with the bolt closed and the dust cover shut. I don't use the 450 for home defense - too powerful for use inside a home.