Easy solution. One click per record side. Each record side approximately 20 minutes
Like @ghdprentice I don't and my turntable keeps track of playing time. Not all styluses are created equal. Then they are also subject to a variety of conditions. The only real way to keep track of stylus wear is to look at the stylus once in a while. Unfortunately, there is no easy, inexpensive way to do this. A cheap USB microscope will not do it. You have to spend at least a grand to get anything powerful and stable enough to see stylus wear. On top of this you need special lighting. You can send it out every so often to somebody like WallyTools, great service but a PITA. Most people just go out and get a new cartridge at intervals like every 5 years.
My own routine now is I rotate three cartridges. Everytime there is a rotation I examine the stylus coming off the turntable. If it were to show signs of wear it would be sent back to the factory for exchange or rebuild. I rotate cartridges every six months or so.