Mason bees are vulnerable to pests (wasps and mites, etc) and if their nesting holes are not cleaned out every year, you will lose bees and eventually they will no longer nest in your bee home.
Go here for more information on management practices: http://lewiscountybeekeepers.org/resourceslinks/mason_bees
Also, you can do a Google search for "mason bee information" and find several sites that also address management.
You can also go on YouTube and search for mason bees and find good videos there as well.
