Serial Mailers or Leads Being Re-sold?

Many agents here seem to write a lot of replacement policies. I also read many posts where an agent notes that another agent door knocked their prospect during the interview, or a few days before or a few days after the appointment. So it would seem that many of our FE prospects are either mailing these cards in repeatedly, or we are being sold the same leads over and over.

Which is it? Do you think these folks are really filling out multiple cards and mailing them in, or do you think that some of these leads are being sold repeatedly to different agents?

EDIT: I also see that somehow

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