[Organizers] Timing of Facebook invitations

I have a question for organizers who use Facebook to publicize their dance events: How far in advance of an event do you send out a Facebook invitation? Sufficient advance notice can give time for some buzz to build as people get to see that other people have marked themselves as "Going" or posted replies. But with too much lead time, people could decide not to plan that far ahead, and by the time the event draws nearer they could have forgotten about it. How much lead time is a good compromise? The frequency of dances might also be a consideration. Sending invitations two or three weeks in advance might make more sense for a monthly dance than for a weekly dance. I'm currently one of the organizers for a dance that runs on 2nd, 4th, and 5th Saturdays, so dances are usually two weeks apart but occasionally only one week apart. A similar situation would apply for a dance that ran on, say, 1st, 3rd, and 5th Saturdays (or Wednesdays, or whatever). I know one series that runs on 1st and 3rd Saturdays and 4th Fridays, so that about once ever seven years they have consecutive dances on Friday, February 28 and Saturday, March 1. Dances could also be closer-spaced than usual if a special-date event is *added* to the calendar (instead of *replacing* a regularly-scheduled dance). Organizers could want to get timely word out for whichever event happens second, but not want to stomp on the earlier one. With a calendar on a regular web page, you can just list all the events, with as much or little special emphasis on any particular ones as you choose. But what do you do about timing the Facebook invitations? Thanks. --Jim