To my knowledge, Warm and Natural recommends minimum of 10". W&N is a cotton batting needle punched to a scrim.
Many Quilters Dream products recommend minimum distance of 8", Quilters Dream poly says up to 12". Unfortunately, quilters dream doesn't list the minimum requirements on their webpage for all their products.
All of Hobbs products are minimum distance of 4". This leads me to believe that Hobbs is offering a realistic minimum distance to maintain both the batting integrity and the integrity of the quilt. But this is JMHO. I am partial to Hobbs batting but I have used QD and W&N both and have been extremely satisfied with both manufacturers. I believe all of Hobbs battings are resin bonded.
If you ever come across an all cotton batting that is not needle punched or bonded the minimum distance given on those is usually 2".