Arcade Time-out
Arcade time-outs are menu or gameplay mechanics which are designed to bring the game back to attract mode if the player abandons the game.
Often remembered as frustratingly short countdowns during hi-score name input, they are mainly used to improve player flow and therefore revenue.
There's no real point of keeping such time-outs in the home version of games.
Menus
Whenever the player needs to make a choice, an arcade game should have a time-out after which a default or random choice is made.
These can typically be set up in the software DIPs in 5 seconds increments.
In-game
If no inputs are registered after some time or if the player stays at the same position for too long, the game might display a warning before an automatic attack or an instant kill is triggered. For example a "GO =>" arrow or a "HURRY UP!" message.
In Mutation Nation, bouncing warheads will appear from nowhere and explode when they reach the player.