There's ways to do this, here's how.

1. On a Hitdef. look for "fall.recovertime =" and add the value "ceil(10+75*fvar(4))" to it. (Remove the quotation mark)

This won't prevent infinite at certain situations (like tight ground bounce), but it works well enough with characters without it.) 

Or you can use:

1. Add this into the move that you want to add decay to.

[State 210, 2]
type = varadd
trigger1 = movehit
var(22) = 1 ;Var value can be whatever you want.
ignorehitpause = 1
persistent = 0

2. Copy and paste your first hitdef into the same state (non counter)
3. Add "triggerall = var(22) < 2" and "triggerall = var(22) >= 2" to the new hitdef. (Refer to image 1 and 2 if you're confused) (Remove the quotation mark)
4. On then new pasted hitdef, look for "fall.recovertime" and set the value to 10 or lower. (Refer to image 3.)(Remove the quotation mark)
5. Add this code below into -2-3.cns. and you should be set.

[State -2]
type = varset
trigger1 = enemy,movetype != H
var(22) = 0

This will force p2 to use the second hitdef if the number of hits of the same move is greater than 2.
This decay works well with moves without any targetstate/forces p2 into custom state. But in case this fails there is one more thing you can do.

(For targetstate only)
1. Add this into the move that you want to add decay to.

[State 1, Var]
type = varadd
trigger1 = !time
var(22) = 1 ;Var value can be whatever you want.

2. Add/replace your targetstate with this code.

;Ground bounce.
[State 8000, ]
type = targetstate
trigger1 = var(22) < 2
trigger1 = movehit
trigger1 = !moveguarded
value = 5825
ignorehitpause = 1
persistent = 0

[State 200,]
type = targetstate
trigger1 = var(22) >= 2
trigger1 = movehit
trigger1 = !moveguarded
value = 855
ignorehitpause = 1
persistent = 0

3. My template will already have both state 5825 and 855. So you don't have to worry about it.
4. Add this code below into -2-3.cns. and you should be set.

[State -2]
type = varset
triggerall = var(22) != 0
trigger1 = enemynear,movetype != H
var(22) = 0

This will force p2 to use state 855 if the number of hits of the same move is greater than 2.
This decay works very well if you want to fully prevent infinite hits. (especially if you add nothitby on state 855.)

It is advised to note down the variables you use for the decay/infinite prevention so you won't get confused whenever you want to update your character again.