You can remain perfectly still for long periods of time to set up ambushes.
When you attempt to hide on your turn, you can opt to not move on that turn. If you avoid moving, creatures that attempt to detect you have disadvantage on their Perception checks until the start of your next turn. You lose this benefit if you move or fall prone, either voluntarily or because of some external effect. You are still automatically detected if any effect or action causes you to no longer be hidden.
If you are still hidden on your next turn, you can continue to remain motionless and gain this benefit until you are detected.