The ozone units can run much longer than that - simply sniff to see if yours is still doing the job. If not, replace it.
To keep it running forever, simply make sure that it has air moving through it. That means air bubbles from the floor, AND the smell of ozone when you first open the cover. Air alone can indicate a broken line - you will get the air bubbles (sometimes more than normal) but no ozone. Without airflow through the unit, it can fry itself quickly.
Start with new filters - ew!! Who wants to share sloughed skin cells with somebody you found on Craigslist or whatever. The regular filters can go 2-4 years, easily. The Tri-X filters can go twice that.