The answer depends on a few things: your workouts, your size and step, and how you care for them.
RUNNING SHOES:
Suggested lifespan: about 6 months, or 300-450 miles. Things that can affect it:
- Running with a heavy gait
- The surface they are used on
- How often you run
- How long your runs are
GYM WORKOUT SHOES:
Suggested lifespan: about 6 months. Things that can affect it:
- How often you work out
- Lateral and explosive movements
- Moving with a heavy gait
- Number of steps you take during workouts