Well I will try to help you as well. I have been using the same thread for upwards of 4 years. They are right, keeping it out of the sun helps a lot. But it may be that your machine just doesn't like that brand of thread.I have that problem. I have a Viking Platinum 770 that likes only Gutterman thread,a Jonome Embroidery machine that will only sew well with either Sulky,Maderia or Mettler thread. if I use any other brand it does not sew well and breaks constantly. I know this as I bought some real inexpensive thread some place on line when I first started with my Janome and was so frustrated. After realizing that it actually was the thread I tossed it out.Now I use a thread conditioner(you can get it at a Joann's or Micheals) if I am having any thread issues.It is a silicone and works pretty good.You can get it in the notions area.
On the other hand, if you are using the same needle time after time it may be that as well. sometimes a burr will form on the needle or it just gets dull after a lot of use. Some people change the needle with every new design(that would be me).I guess I would start with the needle,check the tension and maybe have your machine serviced and cleaned out to make sure it isn't a problem that way.
If it is not the machine or the needle then play with some different brands and see which one works best for you and your machine. Keep in mind that all of it does break to some extent but when it gets to be a lot then there is a problem.
I hope this has helped you out and you solve your thread problem.
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