Let's say we have a level 20 human wizard named Dumbledore. Dumbledore is wicked old. Dumbledore would like to not die of old age, as he has a few enemies left to take care of. Can Dumbledore cast True Polymorph on himself, concentrate for the full duration, and permanently de-age himself into
- A younger version of any other creature
- A long-lived creature (dragon, elf, etc)
And if yes to any of these, will this permanent transformation extend Dumbledore's lifespan? Would doing so permit Dumbledore to repeatedly cast True Polymorph and never die of old age?
Note: Dumbledore could obviously still die of other causes, such as Power Word: Kill cast by a talented former student.