Ok, just to make Doug spew smoke from his ears (humor intended here), here is some new information...
On my first Camino, I wore a pair of Keen Targhee II mid-high's. They had less than 100 km practice wear on them before starting. By the time I reached Santiago, 34 days later, the fibrous mid-sole-layer was showing through on BOTH heels.
On arriving home, I took several photos of the heels and sent them via e-mail to Keen only to suggest that, for the price paid, they might consider changing the density of the rubberoid compound used at least in the heel area. I explained the
Camino de Santiago and the varied terrain.
They promptly apologized and sent me an online coupon for a replacement pair of any Keen boot of equal value. They have one of those "no excuses" warranty policies. I never actually asked for a warranty replacement. They just did it. That is one sign of a very good company.
So, I did two things. I promptly ordered another exact pair of the same boots, soft heels and all, online, from Keen. Also, I sent off my boots to be resoled. Even glued on soles/heels can be replaced. I found the firm on the web. My new Keen boots are still sitting in their box in my closet.
However, they never did alter the tread material on the Targhee II. I have been checking my local REI shop periodically to talk to the shoe clerks to verify this. They did however, come out with a similarly styled, but more expensive mid-high model, the "Durand." This model DOES HAVE a denser out sole material in the heel and sole. On the other hand, it costs an additional USD 45 (USD 180 vs. 135 for the Targhee).
Since then, I've worn the original Keen Targhee II boots on three Caminos, and had them resoled after each
Camino Frances. They were fine after the Porto to Sanitago pilgrimage this year. I am on my third sent of resoled outers. The uppers are so well broken in that I almost NEVER have any foot problems.
Then again, the inner linings are starting to show some wear and tear after about 2,000 Km. So, in another year or so, I may have to switch over to my new pair. For now, I am seeing how many times they can safely resole my original pair of boots. Once I hit three resoles cycles, I will have saved the cost of a new pair of boots.
I personally love Keen boots because the "last" (foot mold) they use to form the shoe portion of the boot, most nearly matches the shape of my foot. I must have a genetically European foot shape, because the only other manufacturer that can make shoes as good-fitting is Mephisto, the premium French shoe maker. FYI, my ancestry is all European. Sadly, they do not make anything that can be used for the Camino. Plus, they are VERY expensive.
Each person must find the best fitting and wearing shoe for them. But, at least for those folks on this side of the "pond" resoling is readily available via the mail. I also know from my Google searches that hiking boots are resoled in the UK too. Just do a web search for "resole hiking boots" or "resole hiking shoes."
It is not cheap. My resoles cost about USD 85 including postage. But that is still at least 1/2 less than a new pair. Plus the resoled boots are broken in and "good-to-go" right out of the box they are returned in. Also, the resoling firm uses actual Keen factory replacement soles. So the result would be the same as if Keen manufactured the shoes. The firm I use also replaces the Keen insole inserts for the price quoted.
The last thing I recommend is to buy shoes from a manufacturer with a "cast iron" warranty. Keen is one such manufacturer. According to Don (above) Merrill is another such manufacturer.
So, buy the best fitting shoes or boots you can afford. Buy them from a manufacturer who stands behind their product; and if you especially like the fit and wearability of the shoes or boots you have, look into having them resoled professionally between Caminos.
I hope this helps.