How long does a portazone last? I

How long does the portazone generator last? I have a portazone with a manufacure date of Nov. 2003 and I was wondering if anyone knows how long it will be continue to generate ozone effectively? when i ozonate water i can smell the ozone so i think its still working ok but i was wondering if they deteriate over time and quit working but its hard to tell because the pump will keep working and bubbling in the water. Thanks!!!! Tweet