Tomorrow starts week nš 81 of Djokovic at nš1. He surpasses Hewitt's score of 80 (total) weeks at nš1. Next one to be matched would be Agassi with 101 total weeks and Nadal with 102 total weeks. The ones still ahead of Djokovic in this stat:
It is interesting because in the 2013 Race, Djokovic and Nadal are almost even ( Djokovic 4140, Nadal 4010 ) and it is possible they both (along with Murray) will fight to finish 2013 season as nš1, and Djokovic will almost sure stay at nš1 till Autumn, nearing Agassi's and Nadal's total weeks by then.
It is possible that, just when Djokovic will be about to surpass Nadal's 102 total weeks (by the end of year) Nadal may be fighting to take the nš1 from Djokovic.
We will see.