Don't fool yourself! Stick to the list! If you think you are going to be able to afford barter items for the things you may have forgotten to store or things that cannot be replaced, build a barter budget. It makes sense to have something on hand you do not need to use to acquire things like medical services, or additional security.
If you budget for barter, consider first, only barter items that you do not use at all! I don't drink coffee, ever. I have stored coffee and coffee flavorings for the use as barter. I can imagine a time when a physician would perform an appendectomy for a good cup of coffee! I have several bags of coffee in rotation as I know, even vacuum sealed, it does not last forever. I also have some extra medical supplies that would make a physicians life easier, like extra stethoscopes and blood pressure cuffs.
Easily stored items for barter are solar power panels, the small ones that charge four batteries, phones, mp3 players and radios are lightweight and readily available online.
Never put all your eggs in one basket or all of your prep items in the same bucket! Fill a bucket half way with barter coffee or grain, wrap a solar charger in plastic, add some medical supplies and seeds. This could be your go to bucket when someone comes knocking asking if you have something in trade for what they have. Keep your reserves, reserved!
This site has a good TOP TEN list for barter itemshttp://alt-market.com/articles/146-top-post-collapse-barter-items-and-trade-skills.
This site has a guide to learn how to barter now while it is easy to learn a new life habit.http://www.manlyadventure.com/how-to-barter/