How long can you keep cotton/poly thread? I have 100s of spools some over 40 years old. They are kept out of sunlight in plastic storage boxes made for thread. I have heard of the tug test where you take a strand and see if it will break easily but that didn't work for me.
About 2 years ago I made pajamas and used a basic blue thread from my stash. Maybe a year later the seam started disintegrating. Fortunately this item was in the family and not a gift to someone else. Even now that spool of thread will pass the tug test. So which spools do I throw away?
I have threads which I had in my tiny sewing box before I married.... 55 years ago.... and sometimes I use them for small projects - none of them hold enough thread for large projects..... and I have some of my mother's threads, too. I wouldn't use hers now, though, because they have memory and antique values to me. Those old cotton reels, as well, smell so deliciously of childhood sewing fun, dolls' dresses and dolls' beds made from chocolate boxes and Mum's lace scraps. I've warned my 'toss-it-out' daughters that they can do what they like with it all when I'm gone but until then it's hands off!!!
I haven't had any trouble with using threads several years old generally and maybe I'll just lucky, but like Noah, I just couldn't throw away old threads.
I don't really think that thread 2 years old should create any problem. I did wonder if the thread of the seam might melt if it were ironed with a hot iron. Maybe it was just the luck of the draw and you managed to get thread from a faulty batch that had imperfections along it.
Darned disappointing though to have a garment come apart like that.
AlmaG.