I have actually bought flannel sheets from Amazon and made quilts from them. I happened upon a sale and wow the king size was cheap and it was a ton of fabric. The quilts are very soft and cuddly.

Now these aren't show quilts and I am sure there is better flannel that could be bought - but you know for my purposes there is no need to spend tons of money on every quilt

I have never used a sheet on the outside layers of my quilt but I resorted to using them for the foundation for my string blocks after the person I send my charity tops to complained about the muslin I used not being liked by her machine. I am not sure I would send a sheet to a longarmer for a backing but I would probably have a go at using one on a quilt I was finishing on my domestic machine if the colour was what I wanted.

I've spoken with a couple long armers and they said if it's what the customer wants them to use then they do. Most customers ask the longarmers first. Also depends on the thread count.

Rules are made to be broken. My quilts turned out better before I knew the rules: prewash. starch, no sheets, no this or any of that. BAH! I try things to see if they work...I was using t-shirt cotton knit and flannel for the backings back in the mid 1970's. No one told me I couldn't and I wanted a soft feel. Try what you think will work and can afford. You'll be happier. The results will probably be better, too.

I've used sheets in the past and never a problem. Sheets are all my longarmer ever uses for backings for her quilts.

My stepdaughter brought me an old quilt that was getting worn and asked if I could "fix" it. I cut it in half to make two twins. She gave me some striped poly-cotton sheets and I covered them on both sides with the same sheets. (I had taken the stripe and cut squares so that I could make an easy pattern with the stripes. That used it all up.) They were in her house for several years before they took a sailboat trip with their three children for 2 years in the Caribbean. Those two quilts were the most used bedding on that boat. My husband and I went to stay with them twice for 2 week stints. Think of a motor home with seven people inside. You can't just open the door and take a walk. A swim, maybe. The quilts still live.

I agree about the gauze like texture of white cotton fabric sold these days...the only brand white fabric I purchased now is Kona

Sometimes "rules" are invented by those selling something. Who knows or remembers when this was started? Remember back in the day, you used whatever you had.

I always use a sheet for the back of my quilts and I hand tie them. I have some flannel that I am going use on my next one for backing. Will see if I like that better.

I think they work fine as long as they are only cotton....don't think the permapress ones would work too well....So far I haven't used any, but I have friends that do and they are quite happy with them.....but they only use cotton. That's important.......