In my experience as a running coach, most runners keep their shoes way past their prime. There have been rules like between 200 to 300 miles or every 6 months as a good time to replace running shoes.
While I think it’s a good idea to have these as the drop-dead replacement dates, truth be told, there are too many factors in play to make blanket statements across all shoes.
In general, if you start to question whether it’s time, that’s a good indication that it’s time for new shoes. Visual cues can also give valuable insight into a shoe’s retirement time. If the outsole rubber on the bottom is unevenly worn, it’s time. If the midsole foam is heavily creased, it’s time.
A word from wise — never wear your running shoes for walking. Only ever run in them. Walking or even standing in them will shorten their lifespan. Save your retired shoes for walking.