Personally I think you could just about argue that 120 years is a generation, at an absolute stretch, because it is the outer limit of a human lifespan. This would correspond with the 120 years as “days of Noah” and bring us up to 2034.
I suspect that the Org would scramble to find a way to extend the generation. Perhaps they would ask for a very old Jdub volunteer to be permanent connected to life support machines for 50 years in order to say that actually the generation is still alive.