I ran through my first set of reagent in about six weeks. Was on vacation at that point and started to get some wierd readings (ca dropped from 450 tom320, which is essentially impossible) for a few days until I got the reagent empty error message followed shortly by no test in 24 hours. Ended up with less than 30 ml for B and C, a bit more for A. Once I replaced them and recalibrated, readings are back to normal. Probably prudent for trident to be set to leave a little reagent, particularly if you are using it to trigger dosing.