Lock Duration Of Behaviours To Set Duration

Hello all,

Im working only on a small titles effect I want to use in videos. Its just a basic text with a behaviour

My question is, how to lock the duration of the 'peek in' effect so when I change the duration of the title effect in Final Cut Pro the 'peek in' effect the duration stays the same.

At the moment if I have something longer with more text the peek in effect (making the duration longer of the title) just looks horrible in slow motion and then you don't see any animation if it is a one worded title for a short duration.