[Illuminated One]

No, longetivity or what the suck it's called doesn't grant you good health.
It just makes sure you're tough enough that you have more time to revel in the pleasantness of a *ucked body part for a longer time. As a general rule of thumb you should ask your local witch doctor for longetivity before you contract a disease.
Except if you loose hitpoints every turn, then longetivity won't stop your approaching death.
A ring of regen can keep you alive with disease for a long time but only a healer can make the disease go away.