Unity How long should a powerup last

This is a question that every game designer has been asking themselves since games began. This all comes down to how you want the gameplay of your game to feel for the player.

I am creating a 2D space shooter, so I would like my speed boost power to only last for about 5 seconds. I have tested this out using different speeds and I like that speed the best. It gives the player a small boost and it doesn’t overstay its welcome.

I currently have the triple shot power-up lasting for a few seconds before it runs out and is disabled. I eventually want this to behave differently. I would like the power-up to last for 5 shots before it is disabled. This means that the player will need to pick their shots carefully before firing.

The last power-up I have implemented is a shield for the player so that they can take a free hit without losing a life. This power-up doesn’t have a limited time span right now. It only gets removed once the player takes a hit from the enemy spaceships.