I see what you mean now.
Try adding 2 fade behaviors. The first one can be called "fadeIn". Fade in time x, wait time 0, fade out time 0. This one is responsible for fading in only.
Second one "fadeOut" with fade in time 0, wait time 0, and fade out time x.
You can use each of these individually by using the restart fade on the correct one when your mouse over/mouse out conditions are met (remember to add trigger once).