Shoes with big foam/synthetic soles break down over distance not time. Running shoes are usually 300-500 miles. Bigger hiking boots are 1000. Even if the upper is fine the sole material compresses and stops working properly. It won't matter what you spend likely. You have to be careful here as people have vastly different use patterns. I run so I go through a pair of running shoes every 6-12 months. Doesn't matter how much you spend or what you buy. It is the use that causes it to fail. Remember that there will be people that say buy X but they might only wear those shoes on the weekend so they will last far longer. The only way to get a longer lasting shoe is to go with a more traditionally made shoe with a leather foot bed. But then you lose the benefits of the modern shoe - immediate comfort, support, etc.