just got one, the 98107. 2 questions as i have never used one before. the manual says to trim the cloth junction and that it can be trimmed 20 times then you need to replace the meter's electrode. how often do you trim this? when it no longer holds calibration? every use? never? also, my instructions say there is supposed to be some kind of sponge or tissue in the cap to hold moisture in it. mine has none. can i just put a little chunk of sponge in there? is this necessary, or just a few drops of solution in the cap will do? thanx!