I like your interpretation; it's made a few links I've never thought of before.
I agree that 'Never Get Old' fits into the drugs/partying category, but I've always taken it to be an ironic comment at the expense of a naive, younger Bowie who believed that he would never age. The album cover expresses similar sentiments, but the disparity between the 'real' and cartoon Bowie are fairly apparent.
Sequentially, I think it belongs before Ashes to Ashes, before the come down.
Fifteen jugglers, Fifteen jugglers
Five believers, Five believers
All dressed like men