Welcome to DC Burnt Toast! We have fun here. You seem like a fun person. It's a fit made in...the kitchen!
Like ahoymatey I have someone who makes sure there aren't that many leftovers. I do try to cook more than the two of us need so that I can build up an inventory of leftovers for later in a week, but the oldest leftover is never more than a week old. Some things won't keep even that long, like fish or other delicate foods. Keep in mind the fresher the raw ingredients the longer the leftover will be good for.
As far as freezing them goes, like others have pointed out, air is the enemy. Use a freezer-safe container small enough to fill. If you want to be extra safe you can wrap the container in a bit of plastic wrap or foil.
Hope you get answers that help ~ and come back often!
"Cooking is the art of adjustment". ~~~Jacques Pépin