Sessions & Tracks : Pro Tools Main Windows : Edit Window : Edit Window Default Length

Edit Window Default Length
Pro Tools lets you set a default length for the Edit window in hours, minutes, seconds, and frames. This is useful if you want to assemble a session of a particular length or leave extra room to expand the Edit window’s work area in your session. The maximum length is 12 hours and 25 minutes at 48 kHz, and proportionally less at higher sample rates. For best scrollbar sensitivity, set the length to slightly longer (a minute or more) than the total session or song length.
To set the default length for the Edit window:
1 Choose Setup > Preferences.
2 On the Display page, enter the value in hours, minutes, seconds, and frames for the Edit Window Default Length setting.
3 Click OK.