Our bodies need oils and fats in addition to other nutrients to be healthy (hey, I'm not a health expert, I don't know all the details, so don't expect a scientific research paper here, just know it's true). Oils make our food better looking and better tasting. Sure, you won't need oil or fat in everything you cook, but how are you supposed to make chocolate chip cookies in your solar oven without a bit of fat to go in them? Okay, I know you can substitute applesauce or ground beans for the oil, but it's not the same, you know it's not. If you're making chocolate chip cookies, I'm coming to share them with you, and I like them with fat!
Fats are solid at room temperature like shortening and butter. Oils are liquid at room temperature like olive oil and vegetable oil. Some oils are better suited for storing than others. The best liquid oils I have found for storage without spending my childrens' inheritance are olive and canola. They keep a long time and are some of the better oils for you healthwise.
When I first started storing food someone told me oils only kept in storage for 6 months or so and you had to rotate them fairly quickly and consistently so they wouldn't go rancid. This kept me from storing oils for quite a while because I was afraid I'd be wasting my money on oil I wouldn't use and then have a bunch of rancid oil in my storage.
Now, the reason oils go rancid is they oxidize, and there are three factors that hasten the oxidation process of an oil: Heat, Light, and Air. When you're storing your oils, you want to avoid warm places, places that get a lot of light, and keep the bottles sealed. Find the coolest, darkest place you can to store your fats and oils. I keep mine on the food room floor. The floor is cement and the room is not heated, which means even in the summer the floor level stays fairly cool. It could be better, but it's the best place I have. If you don't have a food room, think of a place in your house that stays relatively cool and dark, preferably without a window--maybe a closet or a spot in your basement or behind the couch. Think about it.
Okay, back to my oil storage experience. I finally decided I needed to bite the bullet and put out the money for some oil for our storage, so went and bought gallon jugs of canola oil at Sam's Club. I also picked up a few smaller bottles of oil here and there. I put the date on the bottles and put them in closets (I didn't have a food room at that house). I found that the oil actually stored a very long time--far longer than 6 months. I have used oil that is more than 4 years old and it has been fine. What wasn't fine was that after the bottle of old oil was opened, it went rancid much faster than fresh oil. I couldn't use the oil stored in gallon jugs fast enough before it began to go bad. Now I only buy oil in smaller containers, usually the 48 oz. bottles. Smaller is good, I wouldn't go larger than 48 oz. I've found I can easily use the full 48 oz of 4 year old oil before it goes rancid.I haven't had shortening last quite that long--I also haven't been quite as religious about having lots of shortening in the storage as I have with the oils, so I only have one round of shortening to judge how well it keeps. That shortening was about 2 years old and had been stored under my dresser. Didn't work. It was no good when I opened it. Now I have my shortening on the food room floor, but I only keep as much as I'll be using within the year. Maybe you've had better luck?
The results of these experiments are based on oil being stored in an entirely uncontrolled environment in my house in Utah where it's not crazy hot or humid, so your results may vary.
Oh yeah, I keep butter in the freezer. It keeps practically forever that way. I tried bottling butter, but it didn't work for me. If it works for you, that's great. Just don't bottle butter and put it on your shelf and assume it's sealed up good and keeping well without checking it periodically.
Make sure to read the comments--some more great oil information there!