I think that it's a sound idea for the poisons and what not to wear off after one successful use, however the fact they they stay in use until they become successfully used seems a bit drastic. Personally, I would make potions and poisons be used in RP and whether or not they are used successfully depends on the capability of the user. For example, if Rauco soaked Darastix Ui in a poison before a fight, I would have to post that in the beginning of the thread, and if he encountered Tyrion on the field of battle and Tyrion managed to fight on par with Rauco and neither participants receive a single scratch during the encounter Rauco's poison would have to have worn off eventually. So maybe give poisons and potions a duration based on the way they are made. The site could also have a chart of known poisons and potions. (For the sake of space I'm just gonna start calling potions and poisons pots) Players can also create their own pots and choose to donate them to the site list or keep them to themselves so long as they have an accurate account of the pots ability(ies). As for the arrow idea, arrows can be individually potted before a combat scenario or they can be dipped in poison during combat which would, if done well, take less than moments to do. Though pots would have to be limited or if not limited, raise difficulty to gather ingredients and create. Players would also have the option to create threads of gathering rare ingredients in dungeons and what not.