This pairing is a tough to beat pairing in the consumer friendly world. I have been running CSL + EXO for 35 months now on my Mustang. I reapplied EXO when I noticed it was going away, and there has been zero signs of CSL degrading. You will be happy!
Just curious, how did you know the EXO was going away and the CSL was still there?
Since I have the same combo, I'd be interested to know how to identify when the EXO is failing and the CSL is still there so I could do another coat of EXO.
I have applied CSL on its own before so I am familiar with how it behaves vs topping with exo in terms of hydrophobics along with my blower. My Mustang got to a point that reminded me of my wife's DD (CSL only) with water beading, sheeting and performance.