Ph pen service BlueLab

The bluelab pen wants 5-6 drops of the storage solution. I put something like 10 drops and use it for about a month, then tinse tje cap with water and put new 10 drops in. I use growth technology liquids. The pH-buffers, dont use again. But bluelab pen, when used correctly, does not need calibrating too often. I have tested my pen in the last 3,5 years many many times, and it still is correct. Same with the ec-pen.