The 'classic' combat boots like
>>675786 and
>>675759 were made primarely to endure and comfort came second. When you're on the front you can't quickly get a new pair when your boots fall apart, having uncomfortable boots is still better than having no boots.
Now that large scale warfare in Europe has become very unlikely because the Soviet-Union no longer exists, some countries, like Germany, have updated their 'combat boot philosophy' and now have combat boots that look more like leather hiking boots than the classic combat boot (pic related). Note how the sole differs from the Alfa M77. The German boots also have a second layer of soft leather on the inside for increased comfort.
So, classic combat boots will last a very long time if you take care of them properly, but your feet will be much happier if you buy a pair of good hiking boots.