I have been keeping a log since 1991. It's great. I have a history of all of my planes - time flown, where I flew. I keep notes on repairs. I retired a plane that had over 1000 flights. I noted crashes also. I made notes as to what I did on occassion with a plane. For example, I practiced landings or a right hand pattern or touch and go's etc. By doing so, I also know how much time I have on an engine. I inspect the engine inside and out after a preset number of flights or time. I keep notes on the battery recycle times so I know when to replace a pack. Because of this, I rarely have an equipment failure.[8D]