Most experts recommend replacing running shoes about every 300 to 500 miles (roughly 500–800 km). After that range, midsole cushioning usually loses rebound, so joints take more impact even if the outsole still looks okay.
Mileage is only a guide: body weight, running surface, gait, and shoe design change how fast foam compresses. Watch for flat cushioning, uneven sole wear, new aches on familiar routes, or runs that suddenly feel harder—those signs often mean it is time for a fresh pair.