Commercially sold dressing is convenient, but what you can make at home is more cost-effective and often tastes better. Olive oil makes a fantastic base for dressing because it's a pantry staple in most homes and is flavorful, versatile and neutral enough to complement other ingredients. How long will your homemade dressing last? It depends on what you put into it, but a simple olive oil dressing, when stored properly, can last for up to a year in the fridge.

Homemade olive oil dressing, when stored correctly, has a longer pantry life than most other oils because of its high monounsaturated fat content. However, it must be stored properly to retain freshness. Store olive oil in a sealed container away from heat and light. Unless you’re using olive oil immediately, don’t store it in an open container by the stove, as this may cause the oil to become rancid. Rancid oil becomes a health threat even before bad taste or odor is detected. Refrigeration works to help preserve freshness for long-term storing, but oil may thicken and become cloudy. Returning olive oil to room temperature will bring back its fluidity.

A main ingredient in homemade olive oil dressing is vinegar. According to the Texas Agricultural Extension Service, unopened vinegar can last in the pantry for two years, and opened vinegar can last for 12 month. Natural vinegar, unlike distilled vinegar, can produce sediment after three months when opened. This sediment, although unsightly, doesn't affect the taste or integrity of the vinegar. Therefore, a simple dressing made with fresh olive oil, fresh vinegar and salt and pepper can last in the refrigerator up to 12 months.

Adding raw eggs, mayonnaise or mustard to homemade olive oil dressings poses its own risk if stored for too long. Mayonnaise and mustard, the safer options, have longer shelf lives. Opened mayonnaise lasts up to three months in the refrigerator, and mustard lasts for six to eight months. To be safe, check the expiration dates on the bottles to prevent bacterial contamination. Fresh eggs in the shell can last for three to four weeks in the refrigerator, but as soon as they are cracked open and mixed within an olive oil dressing, they will only remain fresh for two to three days.

Pure garlic and pure oil last for months in the pantry, but once the two are combined in a homemade olive oil dressing, the storage time decreases significantly. When chopped or minced garlic is added to an olive oil dressing, it can be stored in the refrigerator for one week. Commercial dressings can last for months in the refrigerator once opened due to the added preservatives, and the acidity from the vinegar in a homemade olive oil dressing may also act to preserve the garlic. However, according to Health Canada, storing garlic in oil in the refrigerator for longer than a week may pose a health risk. Err on the side of caution and dispose of any leftover dressing made with olive oil and fresh garlic to avoid bacterial contamination.