Isn't that the same as Latency? In game, one poison could wait a few rounds to have an effect, inflicting a medium wound, while another could act after ten years?
Also, if wounds penalise all rolls, shouldn't they penalise aging rolls?
This is all very close to how diseases are modelled in Art & Academe. You have an initial Stamina roll to resist once you are infected, a time between recovery rolls, and ease factors to remain avoid worsening or to improve. The effect is part of the disease description.
Mark
True enough. 