I fish 4 -5 tilts at a time, ranging in depth from just a few feet in depth to 30+ feet. I move my tilts at least every 45 minuets, if I am not getting the fish that I want. I try to fish as long a day as possible, so lets say a average of 8 hours... On a slow day that would mean, I might move my tilts as many as 40+ times (almost never happens). I think that I will stick with using a marker, and leave the note pad and spreed sheets at home and at work.
For many anglers that are not aggressive and are happy to wait for a fish to come to them, then your technique will work just fine, I am not going to try to remember what depths each of my tilts are at...