Average # of Days (or Cells) in a Table

Good Morning Experts! Hoping someone can point me in the right direction. I have a schedule with Start and End dates and "x" or "h" to indicate if someone is on call for that week. Using a random name generator to mix up the names, but I want to make sure everyone has about the same amount of time between duty weeks. Looking for a way to easily see the average, number of days between each on call week. That way I can look and say Joe averages on call about every 6 weeks. Hope this kind of makes sense. Open to any ideas (formual, pivot, macro, etc)....Sample attached.

Say you insert a row at the top. In cell C1, use this:
=(XMATCH(TRUE,ISTEXT(Table1[John]),0,-1)-MATCH(TRUE,ISTEXT(Table1[John]),0)-COUNTA(Table1[John])+1)/(COUNTA(Table1[John])-1)

Then just drag formula across the table.

Thank you JeteMC! That will get the job done!

Thank you GregB11...nice and concise.

You're welcome. Thanks for the rep and feedback!

Thank you! It helped me.