It really depends on the batting. Warm n Natural can have quilting or ties up to 10" apart, I think. Mountain Mist Blue Ribbon has to be quilted 2" apart. Check the information on your batting package. If it needs to be closer than your X's, you might be able to place ties in the log cabin blocks.
The whole point is to secure the batting sufficiently so it doesn't come apart and shred internally with repeated washings.