When my players are in their home turf under normal circumstances (decent sized villages with guard outposts in a 1-2 days ride) I don't sweat it anymore. Until they got packhorses it was an issue for the archers, but not really anymore. They usually have a small cart and pack horses with a small arsenal of spare weapons and ammunition.
The fact that everyone uses a different ammo makes it fun. There's a Large longbow, two medium longbows, a medium shortbow, a small shortbow, and a medium crossbow. And the monk uses a sling. They look like hardened mercenaries just from the 600-ish arrows/bolts they cart around. (50 of each, plus an extra 200 medium longbow and 200 small shortbow) Four oversized quivers of arrows plus two barrels of arrows is a decent amount of stabby-pokey.
Right now it's a different story while they're in the arctic regions. Sure, they've got a wizard with teleport but do you want to waste your teleports on arrow runs? Sure, it takes quite a bit of combat for someone to churn through 250 arrows, but 15th level characters do it quite well. It gets worse when you have to leave your pack horses behind. Well, the halfling's okay since his wardog is pretty mobile and has a decent amount of carry capacity free. I'm sure the halfling and elf dumped at least two dozen arrows each into opponents during the last combat alone.