About 142.8 million years if their rate of closure remains constant....maybe by then, we'll know who killed Vince Foster.
I looked it up as well, the numbers I saw say 85 million years.
Another study shows that the Gamma Ray Burst produced by this type of explosion would need to be within 500 light years to sterilize the Earth. 2,000 light years away would just be a very bad day, unless the jets coming from the poles of coalescence were pointed towards us (then its just a mass extinction event).