My father had a bifurcatum about 40 years. It grew huge, because it's a lot of continuously multiplying individual plants. The tree it was on finally died and collapsed. So the bifurcatum was split up into a lot of clumps and mostly given away. Only a few were kept but they still grow on. For the single plant species, I knew of a superbum about 10 years old and still growing strong. I've also seen huge plants of those but no idea of how old.