Refrigerated, natural peanut butter will last for about one year. Unrefrigerated, you should not eat it after two months.

Natural peanut butter has no preservatives, so no refrigeration = microbe growth. You may not see, smell or taste anything different, when you don't refrigerate it, but you can be sure there's some nasty stuff going on in them peanuts.

Besides, if you store it in the fridge, just nuke it for a few seconds to soften it up.

I took a tablespoon of natural pb, nuked it for about 20 seconds and added some DaVinci's Chocolate SF syrup - YUM!