Originally Posted by
pianistat
their 12 monts clock is very exact! So wait for a complete year to pass starting from the date you see your miles posted, and apply 1 year plus one day later.
This is true to the extent that you certainly won't be able to register online any earlier than a full year after miles last posted from the offer, but it isn't the whole story. Many have reported not being able to register even after that year has passed.
At one time it looked as though waiting until the calendar month after miles last posted might be enough. My most recent data point is a family member who last received miles in the first week of April 2014. As of two days ago she was still not able to register again online.