The statement that your drainlines would not last much longer is unusal. If this means that your drainfield is failing, then I can understand it. The observation that the grass is greener over the drainfield is an indication that the water is not draining down into the ground, but is rising to the surface. This is because the field is clogged. If you dig a hloe in the middle of the field, or open the distribution box, you will probably see standing water in the field or water above the exits to the laterals in the distribution box. 

Septic-Scrub(TM) drainfield flow restorer can help in this situation. Please see the WEB page for addition instructions.