I'm a Personal Chef, That means I go to people's houses-cook a week's worth of dinners, and store them in fridge and freezer, sort of like home made TV dinners (without all the crazy chemicals)
A N Y W A Y....
Some of the specific instructions I leave for my clients is "Throw it away after this date: (one week)
But it all depends on what the food is. Some of the food I leave only partially cooked so it will finish off when they heat it. Those have a "throw away date" of only a few days.
I recommend putting a masking tape label with a "throwaway date" on every container of leftovers you have.
Don't keep anything for more than a week even if it "smells good".
Once every month or two take EVERYTHING out of the fridge and freezer and clean it. Then go through and toss the furry jello that you forgot about way back in the back.
Mold makes spores, spores make more mold, only faster.