I have a Summer and Winter set of tires on the toad. They get "rotated" when put on. I replace them when they are worn.
We take the toad in for maintenance at a 5,000-mile interval (per the odometer, ignoring towed miles), except for the transmission fluid change. That's done every two years, as the Honda owners manual says:
If you tow a Fit behind a motorhome, the transmission fluid
must be changed every 2 years or 30,000 miles (48,000 km),
whichever comes first.