Projectors require regular maintenance.  Typically, people think projector maintenance means replacing the bulb when it burns out.  However, there is another aspect which is even more important.  Projectors have air filters which protect the bulb from being hit with dust, pollen, and other air particulates.  When such particulates do hit the bulb, they burn up and leave a residue on the bulb.  Therefore, a filter that goes uncleaned will shorten the life of the bulb due to the problems presented with the addition of the residue.  Additionally, a clogged filter will cause the projector to overheat and shutdown. 

Clean out the filter and dust off each unit once a year.  The projector and bulb will last longer and you won't have to worry about the projector turning off during a church service.