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.
