I would say at least 25, or when you are more or less self-sufficient or in a position to make life changes based on psychedelic insights. At best, psychedelics will offer greater self-knowledge, i.e. this is what's dysfunctional in my life and this is how I need to change it. And sure, spiritual insights can be a part of that, because how you view reality will have an impact on every aspect of your life. But you still have to make actual life changes in order to benefit. In short, psychedelics are not a magic bullet, but an aid, a tool to facilitate change.