It certainly would be for me, depending on the extent, but you can check out once you get a diagnosis. But you might not even get to that diagnosis if cancer or heart disease kills you before that (as the statistics overwhelmingly suggest it will), so you'll always have a net loss of "non-dementia years of life" without fixing those.

Unless you're thinking: you're willing to accept that whether or not you'll ever get dementia in the first place because cowardice or social pressure would prevent you from checking out once you do get the diagnosis. But that's sad and pretty unfair to yourself and others.