It depends on how densely the rest of your quilt is quilted & how often it will be washed. Borders, ideally, should be quilted at a density that is halfway between the closest & farthest apart quilting lines on the center of your quilt. If your quilt is quilted 2" or more apart & it's a wall hanging, you're fine with just doing SID around the perimeter. If it's an adult quilt, I'd probably add an extra short little line of stitching on each side from the middle of the perimeter out to the edge & maybe framing each corner (like a cornerstone), just to give it a bit of stability. If it's a quilt for an infant/toddler, I would definitely add a little quilting in the border so it doesn't get stretched out of shape.