There are aspects of caring for your Otoacoustic Emissions (OAE) hearing screening equipment  that relate to both the external and internal features of the unit.  You already know that you need to protect it from extreme heat and cold and that the probe is a delicate piece of electronics equipment that has to be handled with care.  You've learned to check the probe nozzle for wax and how to clean or exchange it for a new one as needed (depending on the type of equipment). To ensure the accuracy of results, you've also been having the equipment calibrated annually.

What you may not be aware of is that the OAE equipment is also a "computer" that runs on software/firmware.  The version of the software/firmware may appear briefly on the screen when the equipment is started.  Equipment manufacturers are always looking for ways to make the screening equipment work more efficiently.  Sometimes that requires a change in the external design of the equipment.  More frequently,  however, improvements are made in the form of the software/ firmware that runs the equipment, generates the sound stimulus and analyzes the responses coming from the inner ear.
What this means is that you may not need to buy new equipment in order to benefit from improvements.  When you purchase equipment,  software/firmware updates are often included in the purchase price.  Although some manufacturers may send out notification when updates are available, you should not count on that.  Check annually with your equipment manufacturer or vendor to make sure that you are running the latest version of the firmware/software so that you are getting the most from your screening unit.