StrangeDrugs, that is a very interesting take on the interpretation. I tend to, being the old bitch that I am rapidly becoming, try to find comfort in Bowie declaring that it's OK to be old (although, if 'hours..' is any indication, it most certainly isn't).
But the idea that Ziggy's youth has been preserved is intriguing.
On the other hand, if his youth can only be preserved by his being destroyed, it seems to suggest that you die young and remain valuable, or you grow old and become a burden. "It's better to burn out than to fade away," so to speak.
I like beer with my air.