How long does home-made salad dressing last in the refrigerator?

susan g, any oil infused with any kind of vegetable matter needs to be refrigerated. The risk is botulism contamination at room temp.

You don't have garlic in this recipe, but I'll bring up something that surprised me. Garlic in oil has to be refrigerated, and used in a finite time period, because it will cause unwanted bacterial activity.

If you store it at room temp, the walnuts will go rancid. Once you've toasted them, you've made their oils much more volatile and subject to spoilage. I wouldn't plan on storing it in the fridge forever, either. Perhaps making as much as you would use up in a week would be a good rule of thumb. And definitely follow student epicure's suggestion to use the sniff test once it reaches room temp; rancid oils smell like nothing else you'll ever want to smell again. I'm guessing AntoniaJames uses a semi-colon followed by a right close parentheses ; )

in situations like this, when it's unlikely anything has gone bad, i really first on the sniff test, then on the taste test.

Honestly, I just leave it on the counter in a jar and it's fine pretty much indefinitely. This is a salad dressing made from olive oil, vinegar, herbs, garlic, and mustard - obviously anything with cream or eggs wouldn't do so well.

It will last until you use it up. Just be sure to take it out long enough before using it that everything comes to room temp.

Weeks! Maybe even months. The only thing that might go bad is the oil or walnuts and that's unlikely if you're keeping it in the fridge.