How do you track your mileage on your 5th wheel/trailer?

tegu69 wrote:
If your worried about tires wearing out, you could get an inexpensive tread depth gauge and check the inside, center, and outside depths. Check for uneven wear.

The good old penny works very well for that. If the top of the head shows it is time to replace the tire. Or watch the wear bars if your tire has them. But as others have said, unless you have an axle problem age is the factor for tire replacement and most other maintenance on trailers.