We run 3 6' ground rods in line about 10' apart. We generally have fairly damp soil, really dry soil can make a difference.
Same here. We have a sand layer with a clay cap that runs anywhere from 18" down to over 6' down. Ground rods set like yours handle it really well. Others might have to put more, and deeper ground rods in, or more hot with ground lines between them with ground rods spaced at intervals.
Ed
