I assume the apogee and perigee consume more than 10% each, of the 3,600 year orbit. This would suggest 360 years to make the loop. If it is a brown dwarf as some suggest, it would not be moving as fast now as it did 400K-years ago. In any case, it would be between earth and mars for quite a few years and we would orbit the sun some 360 times, passing very close to Nibiru each year. The greatest effects would be in the perigee year. It has also been suggested that the biblical term, "Moon shall turn to blood,,," refers to Nibiru, as it is supposed to be red, and about 5-times larger than earth. At the suggested distance, it would appear about the size of the moon to the eye.
One thing for certain, it won't appear and disappear overnight.
IF,,, it is out there at all...