There is no set time for it to work. Everyone has their own pace. Generally speaking, the more experience and development you have, the faster the process gets. It also depends on what time of day you are doing it, how many hours of sleep you've had if you are using the WBTB method, etc. When I was first starting out, it would take no longer than half an hour to trigger a projection with that method.

You can absolutely do it at night time, but the issue with that is the mind is tired, so it's easy to simply pass out during the attempt. Using this meditation audio at night can serve as a good preparation for the attempt the next morning, and sometimes it can result in projection at night, although this will generally be less common than in the morning, as the body and mind are in a more ideal state in the early morning.

I don't attempt astral projections and lucid dreaming any more. They happen spontaneously now. If I want to project, I simply wake up and let it happen. My body and mind know how to trigger it almost as second nature.