To condition or not condition, what is the answer? It's a question we're often asked -- "Should I condition my thread?" The answer is that there is no absolute yes or no, it's basically personal preference.
If it's something you want to try, here is some information to consider.
The purpose of conditioning thread is to give it a protective coating and make it smoother to work with, reducing "thread drag".
Beeswax used to be the go-to conditioner of choice. The problem with beeswax is that it reacts to nature (freezing or melting), and because it's a natural product it degrades over time, degrading the thread with it.
Thread Heaven (TM) is now the staple of thread conditioners. (I've seen another brand mentioned, but I don't have any information about it.) It is not organic so it does not break down, freeze or melt. The coating helps protect the thread from the sun, mold and mildew, and it uses static electricity to help prevent tangling and fraying as you work.
What to use it with? Pretty much anything that's a thread. I have heard that people don't care to use it with Fireline, but other nylon beading threads, embroidery floss, or sewing threads can all apparently benefit from conditioning.
In fact, the Thread Heaven website has a surprising array of suggested uses, categorized under Around the House, Beading, Bookbinding and Paper Arts, Basketry, Fly Tying, and more. Click on any of the links or Thread Heaven images to go to their website and learn more about the amazing properties of this thread conditioner.