These archers would not have to change to a melee weapon and fight until the enemy troops has broken through their teams melee, the biggest blob has battled, and probably around 50% of all their teammates are dead, and here they'll still get a few crippling shots off...
I have a few times before (considering I suck at aiming (still got great accuracy though of arrow flight)) gotten around three+ headshots before colliding with my first melee enemies, along with a few body shots, and about 50%-100% of my 18 arrows have been used, here I pull out my awesome dadao (which needs to be buffed) and fight the few remaining enemies a bit before either dying, killing a few (or all of them or none but blocking long enough for some teammate to help me) then getting back into the main group of my team.