Heel cups and outsoles on my Diadoras are starting to look a bit knackered, but they have at least 25,000 miles on them, in service since Father's Day 2016. Hopefully they'll make it to 2020, I'd be over the moon to get 4 years out of a pair of shoes.
So long as the shoes are mechanically sound and don't feel weird on your feet, they're still good to go. But if you wanna buy a new pair of shoes, by all means, buy a new pair. No judgements.
__________________
