Depends on your State, but generally there can’t be a ‘rule’.
Some pairings will inevitably last longer than 7 days, so down route has to be an option.
However, days off should be notified in advance, and a reputable company may also specify ‘days off at base’ per month or make some other arrangement.
The rules only require you to be ‘adequately rested’ - having a life doesn’t always get a look-in.
Good luck.