What is the Shelf Life of Foods in the Fridge?

I came across an opened jar of mustard in my fridge while doing some spring cleaning last week. An expiration date is meaningless after a package has been opened, but being a thrifty person, I didn't want to throw it out quite yet. After some fact checking, I created a list of commonly used foods that we open and then wonder how long they will stay fresh.
 

Processed luncheon meats and hotdogs

Did you make sandwiches for the Little League team last week? It is time to throw out the unused meats if they have been in the fridge more than seven days. If the package is vacuum sealed and unopened the meats will stay good for two weeks.
 

Mayonnaise

Store bought processed mayonnaise is made with pasteurized eggs and is good in the refrigerator for two months after opening. Homemade mayonnaise made with fresh eggs is only good for three days.
 

Eggs

Fresh eggs are good for four to five weeks if they are stored on a shelf in the fridge. A handy way to check if an egg is fresh is to put it in a bowl of water. If it sits on the bottom horizontally, it is still good. As an egg ages, air infiltrates the shell and will cause the egg to become more buoyant.

Fish and shellfish

Fresh fish, shellfish, and shrimp will be safe for only two days in the refrigerator. Cooked fish and canned tuna will be good for four days if stored in an airtight container. Smoked fish can be safely eaten for up to two weeks in the fridge.
 

Ketchup and BBQ sauces

The acidity of the tomatoes in ketchup and barbecue sauce allows it to be safely stored in the fridge for four months after opening.
 

Cooked Ham

Not sure how long to keep cooked ham after a holiday meal? The FDA (Food and Drug Administration) recommends using or freezing it within five days of cooking.
 

 Relish

Relish has a long life if kept in the refrigerator after opening - one year! If the consistency, color, or smell changes, toss it in the trash.
 

Salad dressing

I always have worried about keeping salad dressing too long because I am not a big salad eater. Both vinaigrette based and creamy salad dressings are good for up to nine months in the fridge.
 

Pickles

Open jars of vinegar based pickles are good for one year - if you can keep the kids from reaching into the jar and grabbing a pickle with their bare hands! Toss if the pickles become mushy.

 Mustard

I didn't have to throw out my jar of mustard! An opened jar of mustard keeps for a year in the fridge. When mustard goes bad, the smell and/or the color will change unpleasantly.