Beginner roller skating
Four Ways to Read a Dead Wheel

One side smaller than the other. Flat spots that catch once per turn. A square edge where there used to be a curve. And the last one is the sly one: the skate slides on a smooth surface where it used to hold. That fourth sign doesn't feel like wear, it feels like you've got worse - which is why people replace their technique instead of their wheels. Look at the skate head-on: if the profile leans, the wheel is done.
Wheels do not announce themselves. There is no warning light and the mileage figures you find online are worthless, because they depend on your weight, your surfaces and how you skate. What works instead is four things you can look at.
One: one side smaller than the other. Look at the skate head-on — if the profile leans, the wheel is done. Two: flat spots, which you feel as a catch once per rotation. Three: a square edge where there used to be a curve, so the wheel meets the ground on a corner instead of a round.
Four is the sly one: the skate slides on a smooth surface where it used to hold. That fourth sign does not feel like wear. It feels like you have got worse — which is why people quietly rebuild their technique instead of replacing four pieces of plastic.
It is worth knowing that in advance, because the fourth sign is the one that costs confidence. If your stops stopped working and nothing else changed, look at the wheels before you blame the skating.
Keep going: this is one section of the full Roller Skating for Beginners guide — sizing, gear, stopping, and where to skate, in one page.