From what I can see, 3864's livery history has been:

• 4/2000 - new in red/blue livery
  
• 2003? - received branding for a route 305 
  
• 3/2007 - repainted cream and gained Coaster branding
  
• 2009? - repainted pink and gained an Angel logo on the front
  
• 2010? - gained Showstopper branding
  
• 5/2012 - repainted into Northern livery
  
• 1/2017 - scrapped
  

So that's only three (?) repaints in its lifetime.

In comparison, there's the B7 Geminis. I picked a random one from both batches:

3941

• 6/2005 - new in X10 livery
  
• 10/2009 - repainted maroon
  
• 10/2010 - gained Tyne Tees Express branding
  
• 9/2012 - repainted silver
  
• 5/2013 - received TEN branding
  
• 6/2014 - repainted red
  
• 4/2018 - repainted into 2016 livery
  
• 7?/2021 - gained adapted 2019 livery
  
• 9/2021 - repainted into Metrocentre Express livery
  
• Will probably be getting yet another repaint soon now the X22 is no more
  

3964

• 4/2006 - new in red/blue "swoops" livery
  
• 1/2007 - repainted pink
  
• 5/2007 - gained Angel branding
  
• 10/2009 - branding removed
  
• 3/2010 - repainted maroon
  
• 10/2010 - gained Tyne Tees Express branding
  
• 8/2012 - repainted into Northern livery
  
• 4/2013 - repainted green and gained "Festival of the North East" promotional livery
  
• 7/2013 - repainted yellow and gained Real Radio promotional livery 
  
• 10/2013 - livery removed
  
• 11/2013 - gained Children in Need promotional livery
  
• 2/2014 - repainted red
  
• 3/2018 - repainted into 2016 livery
  
• 6/2021 - gained adapted 2019 livery
  

By my count, that's 5 repaints for 3941, and 7 for 3964.

Edit: looks like I was too slow!