in medieval warfare around 1000-1200 archers in the west were not much used, it wasnt untill the english discovered the value of welsh longbowmen untill they started to use lots of bowmen. The value of these longbowmen lay not only in their great skill with the bow but also in the fact that they were rather excellent medium infantry.

I think archers carried like 10 arrows... Longbowmen fired rapidly and far, crossbowmen fired powerful bolts from a short distance (they had long range but short distance volleys packed anough punch to penetrate armour). IF you read accounts from muslims you can see that their volleys on the heavily armoured and densed packed frankish knights had little effect, so I against mail armoured soldiers arrows had little value, however against densely packed ill armoured soldiers like the scottish shiltroms they were invaluable. Where the knights failed to break the schiltroms, the longbowmen just teared them up. So as said before it depends entirely on the sitiuation, type of soldier and enemy. Also in wet places or on wet days where the string couldnt be kept dry archers were rather useless.