When you have things that need filters. You will more then likely be going through many of them. Filters need replaced so many times in a year. You can buy them in bulk if you really wanted to. If you knew that you needed so many in the near future. You can buy the wf50 replacement that you have been needing. However you want to go about buying it is all up to you. Although if you buy more, it would be better. The reason is because you will be paying less on shipping that way. Either way though, it will save you money.