Abstract: A method of preparing at least part of a medical device for application and a medical assembly for preparing or storing the at least one disposable unit of the medical device is presented. The medical assembly comprises a chemical or physical monitoring device for counting and/or displaying a time period of application and/or time remaining before required disposal or replacement of the disposable unit. The monitoring device is automatically activated by moving the at least one disposable unit relative to a second unit of the medical assembly for preparing or positioning the disposable unit for use with the medical device; assembling the at least one disposable unit and the medical device; and/or withdrawing the disposable unit of a storage compartment of the second unit.