Here's an point of comparison: it took Justin Bieber's "Baby" -- the most-viewed music video on YouTube -- 2 months and 8 days to hit 100 million views. The chart below compares the daily views for "Baby" and "Friday" starting on their posting to the day they hit 100 million:
There are numerous other iconic viral videos that have never even hit the 100 million mark, like "Bed Intruder" or "David After Dentist." As we mentioned previously, Black's video exists as both a standard viral clip and a music video with some staying power, which could account for its longer tail, though it's hard to imagine it could catch Bieber's 561 million total.
Something else we've noted in the past is that Black's video has inspired a serious parody and cover phenomenon as well, resulting in numerous alternate-day-of-the-week variations. A number of them have drawn over a million views and there is a video with at least 100,000 views for every other day of the week now:
(May take a moment to load. Watch the full playlist here.)