How many hours do you have to put in to reach BFF status! Well by a study performed at the University of Kansas it takes 200 hours! To go from acquaintance to casual friend it takes 50 hours, casual friend to friend 90 hours, BFF status 200.
Quality of time is also broken down by casually hanging out, joking around, and activities like gaming together. So work friends only count if you put in time outside of the job partaking in the above mentioned activities.
I think they should have also instituted the level "you're stuck with me". I'm friends with many that I've been friends with since elementary school. WELL over 200 hours. A few decades of friendship and I think it's solidified!
If you're curious if your BFF is actually your BFF... they even have a test you can take. (Test)