When I was in the Army we always trained in full combat gear. That gets you used to wearing it so the extra weight isn’t noticeable, and it gets you so familiar with it that it becomes an extension of yourself. I imagine knights of Middle Earth used a similar philosophy. Plus, they were expecting worg attacks on the road and needed to be prepared. They did in-fact face worg attacks, so it’s a good thing they were prepared.
In the movies, the Uruk-Hai definitely marched from Isengard to Helms Deep in full armor without a supply wagon in sight.
Even when the Uruk-Hai captured Merry and Pippin they were running long distance in full gear.
But stamina in LotR is a little wonky. Aragorn, Gimli, and Legolas ran ~130 miles in three days.
Those 3 consist of an immortal elf, a dwarf who are known for their endurance yet complained the whole trip anyways, and an 85 year old Dúnedain, a race of men descended from the Númenóreans, who are known for their longevity and noble lineage. So they’re not exactly common foot soldiers.
Back when we could expect good things from our Octogenarian politicians \s.
But on a serious note, I think the supply train for the orcs was non existent as they were … expected to live off the land…