Choose the interval based on three things: total real time recorded, final video length, and playback frame rate.

Formula: interval between shots = total recorded seconds / (final video seconds × fps)

For 7 hours: 7 × 3600 = 25,200 seconds

Example at 24 fps:

• 2-minute video: 25,200 / (120 × 24) = 8.75 seconds per shot
• 3-minute video: 25,200 / (180 × 24) = 5.83 seconds per shot

So for a 7-hour sequence edited to 2–3 minutes, a shot every roughly 6–9 seconds is a good range.

If you use 30 fps instead, the interval will be slightly shorter. For example, a 3 min 30 sec video from 7.5 hours at 30 fps works out to about 4.3 seconds per shot.

In short: decide your final runtime and fps first, then calculate the interval. For your goal, starting around 6–9 seconds is reasonable.