Give the option to send people into other programs once they have reached the end. For example, if you have a welcome program where you are gathering additional information and behaviors, give the option to send people to another existing program that would further their journey. When someone is new you first want to send them a couple emails, but not have the next program begin until they finish the welcome. Two programs can be running simultaneously for the same contact--I know you can create paths in that initial program, although it would get very complex and making changes would be easier if you could keep program separate and only make changes to the parts of their journey that are needed.