Surviving on a very limited budget, I replace them when the pain of running exceeds the pain of paying for a new pair of quality running shoes (Nike up to now still the most affordable for me) 😅. My best times (I am a masters runner) I ran in 1981 in a pair of army tackies (canvas shoes with a rubber sole, was like barefoot running). Nothing like the modern shoe choices of today. Irrespective of the shoe, my experience is that one must have a basic good foot condition which can take a lot of hammering. It should then also be able to handle an older shoe.

I have severe supination issue on my right foot when I run, so the front right side of that right foot wears down much sooner than the other parts of the shoe and the left shoe. Its such a pain, because it develops very quickly. I have dealt with it by using some shoe goo and applying some of it to that right side to try and build it up again. I've had some success helping my running shoes last longer doing this. Have you ever tried it?