Because we're a small business we don't have unlimited supplies so we have set up a subscription for the soft scrub head (you will receive 2 replacement heads a month automatically and you can cancel the subscription at anytime) this will help us scale exactly how many we need manufactured & make sure we always have enough in stock for subscribers. If you're signed up for the Subscription we will make sure you get replacements sent to you every month. Otherwise, if we're sold out and you aren't signed up for the subscription we can't guarantee when they will be available again. The sponge does hold up very well, but just like any soft sponge, it eventually needs to be replaced.