Steve, after a while, you'll be able to tell what your pool does. Once you can predict with good accuracy what your FC readings will be, You can test every other day or even two. This will change a little with bather load, peak summer time weather etc...but you will get to know your pool, and be able to know exactly what it's doing under most conditions. At first, and until you have a really good feel for it, the FAS/DPD testing really wont cost you much. It will pay for itself many times over when it keeps you out of the pool store or whatever.