How long can fruit macerate in the fridge?
It depends on how ripe the cherries were before maceration but, generally speaking, they should be safe to eat!
From William Sonoma:

Because sugar is a natural preservative, macerating is a great method
for extending the life of berries that are less than perfect in
appearance or just past their prime. Fruit prepared this way can last
for up to three or four days covered in the fridge.

and from Serious Eats:

When it comes to prepping in advance for a dish, time is on your side.
If you're dealing with fresh fruits, you can usually start macerating
up to 48 hours in advance of serving. Dried fruit maceration can be
done up to a few weeks in advance and stored covered in the
refrigerator. In either case, alcohols with higher percentages
(bourbon as opposed to red wine, for example) will help preserve your
precious fruits and berries from spoiling.

When in doubt, I use the good ol' sniff test and err on the side of caution. No cherries are worth getting sick over, in my opinion :)