Should You Apply to a Show that is "Not Currently Staffing?"

My sister is currently applying for PA positions and is frustrated with the number of shows that are already staffed.  But I always tell her, apply anyway.  When you call a production office, you generally speak to an assistant.  Often times, that assistant has no idea he or she (or a fellow assistant) is about to be fired and that the show IS actually staffing.  Attention your cover letter and resume to the production coordinator and send it in.  If the show is already staffed, they will keep your resume on file in case something comes up at a later date.  Also, if your resume is good, the production coordinator may pass it along to another show that is staffing.  I applied to CSI a few years ago and their production coordinator called me personally to say, "I received your resume; we're not currently staffing but a friend of mine on another show is, and I'd like to send your resume to her."  How kind. 

Apply to every show. You never know what might happen.