@starrynight - It's great your mom was able to fix your couch for you. It's always cheaper to do something yourself than to pay someone else to do it for you.
I used upholstery thread to sew some pillows for my couch quite awhile back. I was going to just use regular sewing thread, but when I went to the fabric store one of the sales associates steered me in the direction of the upholstery thread.
I'm glad she did! I can tell the tread I used was a lot sturdier than regular sewing thread. I doubt the pillows I made would last as long with regular sewing thread as they have with the upholstery thread.