I don't carry a heavy load like our soldiers, but these boots were so very comfortable right out of the box.  I bought two pair so that I could alternate keeping them dried out after standing in them for 15-18 hours a day, and I can tell you that these boots just keep on trucking.  I haven't had one issue with them and I've had them for 18 months now.  I've recommended them in person to people and I will recommend to anyone who wears boots for long periods of time (overseas contractors, in particular).  They aren't the cheapest boots on the market but your feet will love them for the extra money.  Love the Lowa Zephyr!