If you got stuck at that age, you probably wouldn't be thinking about how you feel, but thinking about how to get at the cookie jar.
With that said, somehow I doubt the fountain of youth will ever be a good thing, really. If you got stuck at say age 30 for who knows how long, and kept seeing all the stuff happen around you (friends dying, pets dying, thefts, crime, etc), how long will it take before you finally crack under the constant mental bombardment? How long would you spend in a mental institution? You'd need a helluvalot of exposure to the good stuff in life in order to keep going. Or alcohol. Take your pick.
If something like that was discovered and made available in my lifetime, I'd bolt far away and live as a hermit.