Items replentish about every 30-60 mins. roughly. GE's, BSOE's, blah, blah.
If your not seeing them always make sure you don't have a spy bot in your Clan standing in your CH by the NPC all the time with it targeted gobbling all the items as they respawn. /kick
It happens because botter noobs are LF more ways to make adena always, and they wanna resell the GE's for more money outside your Clan.