This is the dump cycle.
Short periods make restores easier because there are fewer partials, but use more tape and time.
Large amounts of data to back up or small capacity tape devices also affect the dump cycle. Typical dump cycles are one or two weeks. Remember that the dump cycle is an upper limit on how often full dumps are done, not a strict value. It violates the limit only if a dump fails repeatedly, and issues warnings in the e-mail report if that is about to happen. For instance, a dump cycle of seven days and runs per cycle of five would be used if runs are done only on weekdays.