I do think the number of interviews you go to depends on how you see yourself competitively. Scores, letters, interview strengths. Also what type of program and location.
For example if you really want to stay east coast but not sure how competitive you are, you might have 17+ interviews and keep them all. If you apply and want to incur the cost, you should. This is not about anyone but you. You need to think of your future and your family, not anyone else.
However, if you know that you are not going to interview or rank a program than drop it.
My last piece of advice as an upper level pm&r resident is you probably will rank more programs than you need. I matched at my #1. However, the 11 programs I ranked allowed me to see what all types of programs offered me and gave me piece of mind about your decision.
I feel bad for those who are waiting just to interview, but those of you with many invites worked hard and earned it. I think it's kind of petty to tell people to give up their interviews on a forum such as this because you do not have many or any. Perhaps you should have worked harder to elevate your stock. Kudos to those that did as many excellent applicants have interviewed at my program this year.