If you incorporate these ingredients in your cooking, your left-overs will last longer:

• honey
• salt
• garlic
• sugar (only in high amounts, according to feedback)
• ginger
• sage
• rosemary
• sage
• mustard
• cumin

Additionally from other articles:

• black pepper
• mustard seed
• turmeric
• cinnamon
• cardamom
• cloves

Acids mentioned by others:

• vinegar
• citric acid
• lemon/lime juice

I just had some harissa get moldy after just a couple weeks in a jar in the fridge. I was surprised. I suppose it implies a lack of the above ingredients.