ones catapotamus has cut up all the extra cacti. freeze thawed 3x, and cooked 3x in water, strained and cooked off all the water, i did not like how sticky it was in the crock, so decided to dissolve it in a "tincture" starting with warm water but was going to also use ethanol or vineagar to preserve the tincture...originaly ethanol seemed ideal...but then i started debating with myself about it...so what do you think ethanol, or vineagar? will most likely be a 50% dilution thing with the water content unless there is some urgent reason that would be not good...

If its just in water its not a tincture, its a decoction
If alcohol is the preservative its a tincture.
For glycerin its a glycerite.
and for vinegar its... what the hell? Is there a word for that?
For vinegar its vinegar

Look at the practical side of it. What volume will you have to consume?
Tinctures are usually so concentrated that only like a teaspoon of 20-40% alcohol is consumed. You cant do that with cactus decoction. Will you be drinking a cup of 20% alcohol? More? Would you want to do that in that scenario?
What about vinegar. If you really dilute 5% vinegar by half will it still prevent spoilage? How much would you be drinking, a cup? Would you want to choke down a cup of half or full strength bitter vinegar that resembles something a yak with a sinus infection sneezed out?
Sugar could be an option. Honey and real syrup doesnt spoil unless some just awesome yeast finds it (I learned the latter when I worked with a super sugar tolerant champagne yeast and my syrups grew yeast hats ). Look up instructions for dandelion flower syrup and just ignore everything prior to when they have their flower decoction in hand.

You could always try your preservation idea on just a fraction of the material and keep the rest in the freezer pending your results.