The ammo, aid kits can be easily found everywhere later on. FYI, even the stashes can provide you what you need to survive and fight against the enemies, but they are not really worth more time and energy on searching them, as long as you're doing well in the early game. In this way the next time, the empty stashes at this location may be refreshed with new ones. Whenever you have noticed that there are stashes available in your map, then just manage to collect'em all. I'm not sure if this is a special design to enhance the game experiences. It's less likely to get booties twice or more at the same location. You may kill tons of enemies but just to receive nothing or a little sources. As the stashes can't be that sustainable as you expect.
Unfortunately, if you're opportunistic and always keeping your eyes on stashes, then you'd better find another way out. Then check out your map, a purple triangle indicates the location of the stashes. You get a kill and loot his body, receiving a PDA message telling you that you have found all the stashes of him. In this section I provide full descriptions, comparitive screenshots and recommendations for STALKERs in-game settings, allowing you to determine your personal balance between image quality and performance. Stashes are the most important sources you need to gain in the stay in Chernobyl. STALKER: Shadow of Chernobyl Tweak Guide In-Game Settings.
