Sleep and Freeze

I have noticed something and I wonder why it is happening.

Ok, here comes

I can sleep 3x the same target before sleep has no effect anymore
I can freeze once or twice (cant be sure it never stays frozen enough to be able to be sure) after that I cant freeze anymore the same number of target with freeze..

well if I use sleep, then freeze, I can only either sleep once more or freeze once more, both spells have a direct link between themselves....

So I ask is that wanted and if yes what is the point of it...I should be able to use those in alternate up to three times for sleepa nd two times for freeze but not I can use only 3x either or of the spèlls.


Mei

Diminishing returns.

Apply 30 second sleep (POINT A) -> wears off -> Apply 15 second sleep (POINT B) -> wears off -> Apply ~7 second sleep (POINT C) -> wears off -> full resist

An invisible 1 minute cooldown timer starts after every POINT. If you wait the full minute before applying the effect again (or in the case of C, you can't re-apply), it will reset to the original duration (30s sleep in this case).

This is on a debuff to debuff basis. Bind has a separate timer from Sleep, Blind, Stun, Heavy, Disease, and probably 1-2 others I can't remember.