For discussion purposes only: 
I'll propose that the amount of extended time, that Spray Waxes might afford to "base Waxes", is:
~Zero...Negligible, at best.
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Assumptions:
-The vehicle is a DD
-The initial Spray Wax application occurs during/or-immediately-after the first car wash session, (from the original Wax application day)
-Car Waxes "adhere" to paint; forms a lattice/shell...they don't "bond/cross-link", as would car Sealants.
-A car Wax film-layer is very, very thin (~7.0 × 10-6 inches "thick")
To continue:
•I'll venture that once the Wax on a DD has cured; and, by the time this Waxed-DD has been driven and received its initial car-wash session; that: the original Wax has already been degraded by a certain degree.
-"The Laws of Decay" are always in effect!
-Then, upon the Spray Wax's application, spreading/wiping, buffing/more-wiping, etc.;
-that there is...essentially...little to no traces of the original (underlying) Wax film-layer left to be found.
-As has been stated earlier:
Basically the Spray Wax becomes the LSP in place of the original Wax.
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Why?
-The typical car Wax = 177.8 nanometers (nm) "thick"
177.8 nanometers = 0.1778 microns
0.1778 microns = 0.007 mils
0.007 mils = 7 millionths of 1" (7.0 × 10-6 inches)
-In other words: Just a few molecules thick.
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A perspective:
Let's be generous and give the CC paint-film 2 mils thickness.
Then:
(2 mils) / (.007 mils) = 285.714286
A car Wax film-layer is ~1/286ths the thickness of CC!
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I'll conclude by asking:
-How can a car-care product as fragile as a car Wax withstand the onslaught of environmental and man-made contaminates; rubbing/abrasion from car-wash sessions...and applications of other well-meaning car-care products such as Spray Waxes?
-My answer is, unequivocally, they can't:
They're easily displaced.
-Your thoughts, comments?
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Disclaimer:
The essence of this post is correct...
but I'm pretty sure that every fact in it is wrong.
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Bob