I can't believe VW still hasn't been able to find a darn fix for this issue. My Mk5 had a sagging headliner, my friend's Mk4 had a sagging headliner, my wife's Jetta had a sagging headliner. Just counting down the days until the headliner in my Mk6 decides to sag.
I just got rid of my almost 20 year old Ford Explorer beater that spent its entire life baking in the sun and the headliner was like new.