It does tire though
The other part of why Agincourt worked so well - the English set themselves up with a forest to the back and a freshly-ploughed field in front. The French could not charge up the field - they had to walk. In plate armour. Through dirt they were sinking into up to their knees.
The ones not injured/killed by arrows were pretty darned wiped out by the time that they actually arrived at the English position...
Cheers,
Ben
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)