We are developing game with moving hero and many static (not moving) speedboosts which speed hero up for 1 second when collected.
We allow user to upgrade speedboost during gameplay for 1$ and that extend speedboost duration to 2 seconds.
From UX point of view and when user upgrade speedboost we wonder if all boosts should give player speed of 2s or only boost which are not yet on the screen should give user extra speed? What do you think?