Minecraft wiki entry for Effect, associated text: When having multiple effects, the effects' timers are reduced by 1 second each simultaneously, regardless of when the player took each potion. This is because they use the same "seconds counter" that "ticks" every 20 game ticks to save memory. For example, if the player drinks one potion and another different potion that doesn't reset the timer 5.5 (or any non-integer amounts) seconds later, both effects' timers subtract 1 second from both of them simultaneously.
When a creeper has an effect and explodes, it leaves an area effect cloud for each effect that it had before it died.‌[Java Edition only]
Using a potion of Leaping II, a potion of Slow Falling, and a potion of Swiftness II, the player can jump a 9 block gap.