These are my Mizuno Enerzy. They are only a few years old, but they survived my 110kg to 75kg, 5km in 50 mins to 10km in 55 mins fitness journey. Its getting a bit embarrasing at the gym when people see the duct tape. Ive already stitched the holes up three times.
How long are running shoes supposed to last you? They are expensive! Are they expected to do this, or should they last much longer?
I'm not sure if estimated distances have much use. Everyone wears different shoes, has a different body, different running style and runs in different conditions and on different surfaces. Shoes will wear differently based on all of these factors and a pair that lasts longer for one person might not last as long for another. I don't pay attention to how far I've run in a pair of shoes and just replace them when they're no longer comfortable or easily repairable. So I would say: if they're causing you discomfort or you're changing your running to accommodate them then it's time to move on. Both of those things could cause injuries. If you're still enjoying running in them then maybe you can wait a little longer.