It is usually a good idea to have a brief clothing stop after about 15–20 minutes to enable members to adjust gear and clothing for comfort, and brief rest stops at regular intervals, usually after each hour of activity. Of course, there will always be unscheduled stops for toiletting, camera opportunities, injuries, interesting flora and fauna, or great views.
When and where to stop will depend a lot on the weather, terrain and how the group is managing. Try to pick a spot that is suitable for the conditions, such as after a steep climb, with shelter and a view. During the pause, circulate and chat with the members of the group, and take whatever action may be required to deal with any issues.
A stop for lunch is not just a stop for food and drink. It is an important event and enables members to rest, take photos, wash or air their feet, change their socks or have a nap. It also enables you to review the events of the morning, have a good look at the map and make any necessary changes to your plans.