Short answer: reports and several studies suggest benefits are often strongest in the first weeks up to roughly 90 days after a psilocybin or truffle session. Responses vary widely, and I cannot verify this for everyone.
After that, the trajectory seems to depend on integration and ongoing habits. Deliberate follow-up such as reflection, supportive conversations, sleep, movement, and reducing stressors may help maintain what was gained, while lack of change is often linked to fading effects.
For context, see this summary of a recent JAMA study that observed rapid effects early on. If you proceed, consider making the most of the first 90 days for integration and support. Take care.