If something like the length of time for putting the fire alarm system on test isn't in the publications like NFPA, IFC, and others, you have to look for guidance from other sources. Start by examining your responsibility when the system is on test.
Whenever you "place a system on test", you are personally taking the liability of making sure the fire department arrives if there is a fire. Remember that placing a system on test means that, if there's a fire, no one else will contact the fire department. Walking away for the night doesn't take away that liability; you personally are responsible to make sure the fire department will arrive if there's a fire.
When you're concerned about leaving the system "on test" when you aren't testing the system or maintaining the system, check with the Authority Having Jurisdiction (AHJ). The AHJs are quite a number of people, see:
Just Who Is the Authority Having Jurisdiction (AHJ)?
In essence, one or more of the AHJs can give you guidance on the length of time for the "on test" period. Talk to them, especially talk to the fire marshal.
The National Fire Protection Association Code (NFPA Code) and the International Fire Code (IFC) are publications; the government is the law. The fire marshal is a representative of the government, so the fire marshal can give guidance from the point of view of the law.