Reeds tend to last for roughly on average 6 months, so we therefore advise to purchase new reeds every 6 months to keep the scent throw of your diffuser at its best.If you also decide to purchase a refill scent for your diffuser and the new scent is different to the old scent then a new set of reeds will also be needed to ensure the scents don’t mix, and potentially causing an unpleasant scent. These reeds are sold in a set of 7, ideally for our 100ml diffuser.