I have my processor "set" to notify me at 1500 blocks, at which time I change the paraffins. I usually run 500 in the other solutions (same notification system) before changing. It works for me! Sally Breeden, HT(ASCP) NM Dept. of Agriculture Veterinary Diagnostic Services PO Box 4700 Albuquerque, NM 87106 505-841-2576