Carrier oils have a shelf life of 3-6 months and need to be kept in a cool dark place, or better still refrigerated after opening.
Essential oils last a lot longer unless they are citrus based - if they are being opened daily they will only last for 2-3 months. Making sure that they have dripulators in the lids when you buy them does slow the process down a lot.
Now oils like Sandalwood and Patchouli will llive forever and improve with age - in fact with purchasing these oils, the older they are, the more they cost.
Vitamin E will keep them a bit longer, but again that would depend on where you have it when you're not using it, however every time you open the bottles they will oxidise a bit more.
If you like having your bottles of potions out in the open, the best bet is to make it up in smaller quantities, keep the carrier and essential oils in a cool dark place and mix up a new batch when you're ready.
Here in NZ it's not too much of a problem as we don't have airconditioning or central heating in our homes and our average daily temperature is 21degC in summer, 13degC in winter, we just need to keep them out of our very bright sunlight.
My manufacturing storage room is around 14degC and my carrier oils are usually only in stock for max 4 months.
What I didn't mention further up is that you should make up any formulas in dark coloured glass bottles if you want to keep them for any length of time as the properties of carrier and essential oils absorbs chemicals (including xeno-oestrogens) from the plastic of plastic bottles.
If you are concerned about safety and oily hands, Plastic is fine if you are only make up enough for a week at a time.
Manufacturer of Natural Bodycare products, and naturally red Type 3A Hair