Originally Posted by
wroomwroomoops
Umm... that's kinda an obvious statement, isn't it? The question is: WHEN is EOL for a particular tire? None of my Schwalbe tires had ever flattened on me. The ones I've ridden the most are the Big Apple - I have almost 3000 miles on them by now. The Marathon Plus mentioned above, have much, much, much better puncture protection than the Big Apples.
When you notice your tire has a broad, flat patch where it contacts the road, it's getting old. Or if you see separation of the outer layer from the inside(near the bead), it's time to get new tires. If you're just cruising around town you could probably just keep the tires until they die completely. But think about it if you're flying down a hill; would you want to have a blowout?
There are liners for tires that'll help prevent flats. Spinskins is one. Cheaper than buying new tires.