There is no hard "limit" on audio message length submitted by fans.
If you need longer recordings, feel free to record a long message on your fan page as a test. It will probably work.
That said, we officially support 10-minute audio messages.
We say this only because we've extensively tested this 10-minute duration.
For example, for longer audio messages (e.g. over 20 minutes), sometimes the upload process will timeout due to the larger file size, especially on slower internet connections.
Also, our automated transcription service might not work on longer audio files. We use OpenAI for our transcriptions, and the technology doesn't always work well for longer audio messages.