As long as water hasn't been introduced into your shea, it should be fine and shouldn't have grown any microbes. I don't remember the shelf life for shea but if
it had gone rancid, you'd probably have noticed really quickly when you opened it. 
I should mention that I'm learning, too.
What's the maximum use level on your FO? Adding 1/4 t to 4 oz is 4% and some FOs have a MUL of 4% in creams and lotions. Others go higher, for example, I have an FO which states usage up to 7.9%. I've seen one where it was up to 20%.
Also, you have to think about sensitivity to fragrance. Some people are very sensitive to scents (sinus headache
) and their skin can be irritated by the FO.
Another thought!
If you're going to be selling, you'd want to use the minimum amount to get the scent you want in order to optimize your profits. You might want to separate some finished product and in each sample put a different percentage of scent. Perhaps a sample that has 2%, 2.5%, 3%, etc until you find the amount where the scent is to the intensity that you like.
Or just put a 1/4 t into 4 oz, let it sit for awhile, check it later and add another 1/4 t and so on.
It does take awhile for a scent to marry into your product. After I've added fragrance or EOs to something, I can't smell anything for awhile. It's like my sense of smell has been overloaded so I go off to do something else. Then I come back a few hours later to check the scent.
It's also a good idea to have some unscented product around just in case someone likes the butter but doesn't want it scented. I have a friend who's like this. She wants the creams and lotions but she can't stand fragrances because they give her migraines.
EOs actually take a couple of days to settle into the final aroma. I was doing an experiment with citronella EO to see if I could use it in a lotion since I've read it's an antiseptic and good for oily skin. I blended it with clary sage and lavender EOs. Oooh! stinky, stinky! However, two days later it smelled great...not for a lotion but it will be a great scent for a candle.
I convert my measurements into grams and milliliters so I can be more accurate. Here's a link to a conversion site which might help you. I use the weight and volume links. Awhile ago, I made a table of conversions of the sizes that I generally work with so I wouldn't have to stop and figure out percentages, etc. I'll find it and post it later if you're interested.
http://www.sciencemadesimple.net/conversions.html
I don't want to insult you by telling you something you already know, so please don't be offended by my post.
