Your
THREAD determines what needle size to use NOT your fabric. This is the case for LA and DSM. That said you may wish to choose a thread you can use a smaller size needle with for a Batik quilt top. I only use a size 18 when using King Tut thread. When using Glide thread I can use a size 14 needle. I also use a 14 when quilting with silk, Invisifil, and Bottom line (which I have used as a top thread). I use a size 16 when using Isacord, So Fine and most other 50 wt threads (Glide being the exception). When I quilted my Batik Block swap quilt, I used invisfil thread and a size 14 needle.
http://www.quiltingboard.com/picture...t-t221823.html
I change needles with every bed size quilt unless I have done a panto, then I do two quilts. I may do several smaller items before changing. I keep a log on a bulletin board in my quilting room notating date I put the needle in, size of it and what I am working on to help me keep track.
Here are several good articles on needles by Dr. Bob at Superior threads
http://www.superiorthreads.com/educa...hread-to-shred
http://www.superiorthreads.com/educa...-needle-codes/
http://www.superiorthreads.com/educa...rt-mr-needles/