45-60 minutes usually, depending on traffic and which hotels they stop at.
You can find more information here, including time tables, however it is my experience it never runs on time. When they arrive, there is always at least one guest where there is an issue with the ticket. And the bus drivers often take a break when they have checked all the tickets. Not sure if this obligatory for them, either way, they don't announce it and just leave the guests waiting.