It really depends on the size of your tank, how deep you dive, and how heavy of a breather you are.
We normally use high pressure 80 cubic foot air cylinders with 3300 psi each.
For each video we usually dive just one tank as we tend to always get enough footage for a great video.
Our normal time in water is 40-50 minutes 0-40 feet deep with plenty of laughs and interaction in-between.
When we dive to deeper depths like 100 feet, our dives are normally 20-25 minutes.