I never double stitch seams, just use a shorter stitch. I do back stitch when I am piecing together a block and the start/end of the seam will be on the edge of the block. I've found that the very ends of the seam will separate a little until they are secured by the next block, sashing, or binding. I prevent this separating by doing a 2 stitch back stitch. It isn't a big deal if I have to rip the seam out. It also saves time and frustration putting blocks together when the very edge of the block is still together, especially whe dealing with triangluar pieces cut on the bias.

Do I want to make a quilt twice? No! I do not back stitch either. Just use a slightly smaller stitch on my machine.

No...I have never double stitched a seam....and also don't back-stitch unless it is the final part of the quilt being added (border)...all seams get sewn across, so back-stitching really isn't necessary...at least to me.
If I double stitched seams, would take twice as long to make a quilt...don't have time for that!

If I am chain piecing then I do not double stitch or backstitch. When I am making a large block with multiple pieces in it then I make sure all the seam ends on my finished block are backstitched on the ends that way if my blocks sit a long time or get tossed around I don't have to worry about them coming apart on me. If I am piecing satin or silk I do double stitch my seams just for safety.

Make your stitch length between 12-20 per inch, whatever your machine will do. Tighter is better that a loose stitch. I chain stitch and do not back stitch.

Do not double stitch, but do use a smaller stitch length. Before I layer my quilt I will stitch a scant 1/4" around the edge so the seams don't pull apart.

I would think double stitching would make less "crisp" seams and make you less able to get a really flat finish when you iron. I don't double stitch, unless, as someone else mentioned, I goof up and need to stitch again, a bit bigger seam.

As to LAQ back tack: the quilt is put under some tension on the bars to keep it taunt-no wrinkles. This could pull out a seam that might be loose. So stitching around the top or back tack seams.

For double stitch; I like 50-60 wt thread so that when pressed the seams are crisp and aren't folding around a heavier wt thread. Putting in 2 rows of thread would compound the wt of the thread making the fold on the seam larger and potentially loosing more fabric in the fold. In the past, I often read to use a "skant 1/4" due to the fold over the thread. With 50-60 wt thread "skant" isn't necessary.

When my daughter started quilting at age 10, and I was a newbe at quilting, her seams were a little uneven and the quilts were under quilted. With use and laundry, the seams were tugged back and forth and did come apart. Once we got past that, there's been no problem with seams coming apart. We fixed the problem, not the symptoms.

I never double stitch. I do backstitch some seams at the ends if there could be special problems. If you use good thread, double stitching just weakens the fabric, no benefit.

I have only made rag quilts. Normally I don't back stitch. But I am still new to all of this, and have learned a lot from this thread :) My boyfriend recently spent a week in the hospital after a surgery and I have been working on a special rag quilt for him (with his favorite sports team as the theme). Since he is a big beast of a man (lol) I did back stitch on this rag quilt because I know he will be hard on it, and it will be taken along with him to chemo treatments and future camping trips and such. Hes a big lug so I figured i'd better do what I can to make this blanket a bit tough