Remember to check for mold every so often
You can freeze that jar, oil and all, and it will keep them wonderful for years. But if you just have them in oil, natural deterioration will occur and eventually mold. Because I grow my own tomatoes usually, mold does not occur quickly. But if your MIL got them from the store, they could have been a week or more old already. Just keep checking.
On the other hand, since we use them in salads, pizza, and ground up with parmesan cheese and roasted garlic as pesto for pasta, a jar lasts little less than 2 weeks at my house.
