Hrrmm, I double checked that information, according to Wikipedia it has a lifespan of about a half an hour. But the reference in the Wiki entry sources no sources for this information, nor does the site that I found that says it will last three days, leaving a gapping whole in the truth, at least that which is established by data rather than hearsay.
According to what little I find, OSHA has a .1 PPM limit for ozone concentration in the air in a workplace, which is odd because the site that I found that said it lasts for three days said that there are no interior limitations set up in law, and sensative individuals will have problems at .01 PPM. This is absurdly low, and even at the half hour duration should not be allowed to be outputted by a device for a long period of time.
Again I'll say simply.. It's so much easier just to use good filters than try ionized air filtration as good filters are required regardless of weather or not ionized air is used as ionized air does not actually clean ANYTHING, it simply acts as a coagulant or reactant to. Modern filters are so good, I wouldn't even considering ionizing air generators, simply because there's no grounds for their use.