I've read where bluegrass may require over-seeding every two or three years to help keep the lawn density intact because bluegrass dies after about 6-7 years. First, is this correct? Second, I normally apply Dimension as a pre-emergent to help control crabgrass. With fall bluegrass over-seeding, I assume that Dimension is out of the question until the new bluegrass is established. I understand that Dimension can be used as a post-emergent for crabgrass, but thought I'd throw the question out there for opinions. Thank you.