Tyre wear is different for every person as it depends on a number of things. I.e. The road surface, your tyre pressure, how much you walk it, the heat of where you live. A stroller used in an air conditioned mall will wear a lot slower than a stroller used on gravel/sealed roads in hot areas. It also depends on how much weight is carried in the stroller.
The tyres are a soft and smooth tread designed for walking and a run every so often.
The tyres can be easily replaced. You will need to purchase a new tyre here - https://www.edwardsandcobaby.com/spare-parts/oscar-wheel-parts/oscar-tyre/
You can fit the tyre yourself following this video, or your nearest bike shop will know what to do.