Devils Ivy

Does anyone know how long these live?
This is over thirty years old, is fed occasionally, watered regularly and seems to be still thriving. More than that, it's like a Triffid,taking over a whole corner of the lounge, hiding a picture and some admittedly ugly wires.
I know its minimum age because,while I was working on the Gardeners Question Time radio program,  on behalf of Mrs T  I asked one of the experts why so few of the leaves were variegated. "It isn't getting enough light so it'll never do any good", was the answer!