Quilting stitch density
Is it ok to only quilt 5 inches apart as instructed on the quilt batting package?
I wouldn't recommend it. Personally, about the maximum distance I'd put between lines of quilting is about 3 inches, and even less distance for a quilt I expect to be used.
A lot of our 'go to' quilt battings today--Warm and Natural and Quilter's Dream--are needle-punched...little needles are used to twist the fibers of the quilt batting together, usually onto a scrim.
These battings are very stable. Many feel like thick fabric. In fact, there are patterns that use Warm and Natural as a fabric to be sewn with. Warm and Natural states on the packaging that its cotton batting can be quilted up to a whopping 10 inches apart. (OK, they don't use the word 'whopping', but 10 inches IS awfully far apart for quilting stitches!)
What the quilting distance stated on the batting package is really telling you, is how far apart you can quilt without the batting falling apart.
Sounds good, right?
Except, I don't think that they're taking into account both the wear and tear on quilts AND
the fact that quilts that are used are also washed.
How will the quilt be used...
A quilt that hangs on the wall gets little wear and tear. The biggest concern is whether it will start to sag as it hangs year after year.
More stitches will help keep it stable and minimize sagging. (Cutting your borders and backing on the lengthwise grain from top to bottom will also help, as will using a stable needle-punched batt.) A smaller wall hanging could get by with less quilting than a larger one because of its lighter overall weight.
A quilt used on a bed is pulled up and made regularly. All that pulling puts a strain on the stitches. Adding more reduces the strain on each individual one.
A washed and wet quilt is heavy. Again, the less quilting there is, the more strain there is on each individual stitch.
Stitches under too much strain break.
So I recommend that if this is a quilt that you'd like to have last, add more quilting. Think of the antique quilts have lasted generations that are still in good condition...usually they have a considerable amount of quilting in them. No stitch carries too much of the weight of the quilt.
For more information, I've listed some of the common or 'go to' battings on the page Quilt Batting and Machine Quilting Distances
Thank you for your question. I hope this information has helped.