Mayonnaise-based salads like tuna, chicken, egg or even macaroni taste better after a day in the refrigerator. But, since they're mayonnaise-based, make sure you store them properly. You don't want bacteria growing in your salad as the flavors marinate and develop. These types of salads are typically served at picnics and potlucks where they may sit out for hours. To prevent bacteria from growing, you should make sure the salad's back in the fridge or on ice after no more than two hours. If it's out for longer, you don't want to press your luck, so it's probably best to toss it. With the proper care and storage, however, these salads can last for up to four days.