If you increase the number of friends/occupants living in your town (basically dependent on vacant establishments), you’ll eventually earn the option to send these "excess" heroes on patrol (much like expeditions).
It might take a while, but when your heroes return, they will bring back a certain quantity of items with them. Items like seeds to plant in your fields, or starters for your fish farms. Heroes that will be enlisted to perform patrols however cannot participate in battles or work in the fields as long as they are away on their “Patrol” mission.
Take note that there is a limit to how many Friends/Heroes you can enlist in patrols. Your patrol team requires a certain number Friend Costs depending on the heroes you wish to enlist. At the same time, percentage of success and number of hours it will take to finish each patrol is dependent on the individuals included in the patrol. Each hero or friend to be enlisted has its cost, so make sure to put together a team that you can currently avail.
Each mission also has a default duration to complete. For every hero you enlist to join the patrol, they individually deduct to the time it takes to finish the given mission. Higher ranking heroes deduct larger time compared to lower ranking heroes, although they usually take more slots in the "Friend Costs" to enlist.
On the example image above, we've already reached Rank 8 in the game and yet we are only allowed to enlist heroes (to participate in the patrol) with a total of combined Friend Costs not exceeding 17 points (as indicated by the "Friend Cost 0/17" on the upper right part of the screen). Each of the available heroes in this image show how much deduction (in minutes) each participant can contribute when enlisted in the patrolling team.
Check the next page (Leveling Items and Where to Get Them) to see the list of items to earn in every Patrol mission, and the number of hours they take to complete.