I was getting ready to purge my thread drawer but that's a great idea to use for the basting. Thanks!

I do not know what is considered old thread but some of mine are over 30 years old and were my Mothers, I use them for basting only. You can do the 'tug test' which is helpful also.
Gal

I use older threads for basting or zigzagging edges before prewashing.

Good idea about the zigzag edges, I didn't think of that one.

Gal