Can alcohol extraction be used to draw more of the spice flavors out in chai tea concentrate? I make chai concentrate by:

Quickly boiling ginger puree twice (each time for about 20-30 minutes).
Boiling the spices (bruised/coarse-ground) for about an hour, removing the liquid, then repeating with fresh water several times.
Concentrating the result of the spice steeping by simmering it uncovered for several hours.
Brewing the tea seperately (two steepings of no more than 5 minutes, allowing the leaves to rest in between infusions).

To clarify exactly what I'm asking:

Could I add grain alcohol (Everclear, etc) to the spices during the last steeping to pull more flavor out of the spices after they have already been infused with water several times; or would it make more sense to just do a separate alcohol extraction, then add it back to the finished product?

I've read that much of the flavor in spices cannot be extracted with water, and must be extracted using a stronger solvent. I don't want to just drop alcohol extractions into my water and call it chai though, so I thought it might work as a final step to squeeze the last of the flavor from the spices.
It seems that I never get as much flavor as traditional brewers who use milk at the beginning (likely due to enzymes in the milk was my assumption) so I thought I could science a way to do the same without adding the milk to the equation since milk is obviously not stable enough to store for long periods of time
Your flavors can be grouped in water soluble and oil soluble. Alcohol now is a mixture - some oil soluble flavors are also soluble in alcohol. These are phenylpropanoids, like Coumarin or all flavors that are themselves based on alcohol, like Hexanol. Alcohol is not a better extractor for flavors, just one with shared properties of water and oil, without covering the whole range!

Now we get to the core of your question: 

Those flavors, that are dissolved in alcohol/oil, are much more stable in alcohol/oil than in water. What you smell during brewing are actually oil soluble flavors that went: "I'd rather dissolve in air than water." When you use boiling water, you are losing flavor that could have been extracted with alcohol.

In order to pull most flavors out of the ingredients, you should therefore first extract most flavors with alcohol and then use boiling water. Also, there is no reason to not use fat/oil, too. While milk is unstable, fat itself is very, very stable. If you ever get one of those Asian cup noodles, you will notice that there is a small packet with fat inside together with dried spices. The fat is not there to increase the nutritional value, but contains the oil soluble flavors.