GrogNerd, thanks for asking. I can only speak from my experience, so here it is: well aged Apple Jack is a major panty dropper. I learned the hard way on my first time-lapse consumed bottle of A-J, (no, smart a$$, not about panty dropping) I cannot say how long it was from the opening of the flask I aged it in until it was consumed, a month maybe, it could have been longer. The person I gave a sample to was nothing short of amazed, honestly, and wanted the recipe. Please forgive my ADHD, I get lost sometimes...
I suggest putting it into as small of bottles that are practical for you to use, as it will oxidize and no longer be nectar of the gods quality. Granted, if a 12 oz bottle will get killed in a week or so, I wouldn't worry about oxidation.
As far as back sweetening goes, based on the potential ABV after freezing, with proper sanitation I don't believe there would be a big chance of an infection with adding bottled juices. I generally ferment in the one gallon jugs the juice comes in for my experiments.
Recipe sort-of, pour 16 oz of juice out of jug and into container of your choice.
Pour 1 can of cranberry/apple frozen concentrate into jug, add 1/4 tsp of boiled nutrient, mix well and pitch yeast. I don't hydro my ciders, so I can't give you specific numbers regarding the gravity. I have tried many yeast varieties over the last couple of years, and my solid favorite is Red Star Pasteur Red. If you want high ABV% ciders, this yeast will do it. I like the strong flavor of fruit up front at the end of fermentation, and it is very forgiving during fermentation if temperatures fluctuate slightly. I always have 1 or 2 empty sterile jugs on hand from previous batches of cider, so I have somewhere to put the 16 oz pour off from the multiple jugs. Four one-gallon jugs give 1/2 gallon in jug #5, so I add 1/2 the regular dose of frozen concentrate. By adding nutrient, fermentation may only last 4 or 5 days. Then pour off 12 oz into jug #5, and add a 12 oz can of frozen apple juice concentrate, shake well, and wait another 4-6 days (estimated) until time to add can #3. Same deal, pour out 12 oz into jug #5, but this time, sample the cider at day three or so, and when just slightly sweet, place in freezer, and wait for separation of ice and alcohol.