Storing candied cherries/fruits

I made Cherry & Toasted Almond ice cream over the weekend (Lebovitz's recipe), and I got to thinking about making a larger batch of candied sour cherries while they're still in season, and storing them for later.

I know that the syrup used in candying them is hydroscopic, and I can steam/boil the mason jars during the process to maintain sanitation, but how shelf-stable are they once I crack open the jar? Do I need to add alcohol? How much?

Given how good that almond/cherry combination tasted, Amaretto seems like a natural choice. My worry, though, is that it will thin out the syrup, and heating it will boil out the alcohol faster than the water. So should I reduce the syrup until it's even thicker and goopier than usual before adding the amaretto? How much do I add?

Here's my rough plan:

1. Set up the steaming station with the mason jar & lids.
2. Prep the candied cherries as normal, but instead of draining and separating the fruit from the syrup, pour the entire amount into the now-sanitized mason jar while still hot
3. Put the full mason jar into a the steamer (lid off) and let the syrup continue to reduce
4. Remove the reduced mixture from the heat, and stir-in the amaretto.
5. Seal the jar with the sanitized lid.