I have a question for everyone: what type of backing do you use? I use whatever I have freely available ta the time, but today someone told me that I should only use a flannel back if I quilt a flannel top. Now, I’m think this is one of those, “Don’t use polyester thread because it will tear through your quilting fabric.”, kind f scenarios. Anyone have any advice on the topic? I’ve been mixing up what ever kind of backing
Eric The Quilter 
I wish I knew the answer to this question – I’ve never heard this before either. Hopefully you’ll get an answer and we’ll both learn something new!
I use either one, depends on who the quilt is for.
Most quilts I finish for myself or gifts have flannel backs. I shop for great flannels year-round, and buy in 4, 6 and 8 yard lengths for backs, pretty much exclusively.
It’s your quilt. Use whatever you want.
What nonsense. Flannel is ideal for backings. They just need to be washed first because it shrinks much more than cottons.
I second Ragna’s comment. I have often used flannel on the back of quilts that had regular quilter’s cotton tops, with no problems. I look for sales on good quality flannel sheets (love LLBean’s!) and store them until they are needed. Don’t know where that person heard that, but they are most definitely misinformed!!
I have a friend that uses everything from quilting cotton, to flannel, to fleece. I don’t think it matters so long as the top and backing are preshrunk.