Ok this is how these triggers work: If not defined explicitly, a floating text will remain forever. But since not everybody may want this to happen (i.e. Evasion > "Miss!") so blizzard added a lifespan to floating texts.
"Floating Text - Permanent/Expires" tells a text to become inactive after being expired which means after having lived its "lifespan". If you set i.e. the lifespan of a text to 5 after you have created it, the text will instantly become invisible after 5 seconds.
"Floating Text - Change Age" changes the "age" of a text, so if we for example set the age of the text we created earlier to 4, it will expire after 1 second.
"Floating Text - Change Lifespan" should now be clear, it sets a new lifespan to a text. I don't know how this function affects its "age", so I would set its age to 0 after calling this function.
"Floating Text - Change Fadepoint" is also very important: Once the life(span) of a floating text, the text will reach its fadepoint and start to become old and weak and fade away (lol). If we have i.e. a lifespan of 5 and a fadepoint set to 4, the text will be normally visible for 4 seconds and then fade away over 1 second.
