One dark issue here is that you can surely let yourself to be immature towards the age of 35, but for women it becomes progressively harder to have children after this point. Males have it easier, but if you plan to have a "normative" family with small age gap between spouses, these problems are also yours. Quality of the offspring also suffers somewhat, though this may be offset by superior medicine and post-natal care.

That, or exchange a prolonged youth for having effectively no adulthood, while also moving your society in unsustainable mode*

So our social behavior no longer matches our biology, in which by a quirk we (at least women) are only fertile for around 1/4 of our total life, and less than that in socially acceptable fashion.

* Caveat emptor, perhaps it would be great if we could deflate population of most countries by having low birth rate for a while, but this is not what we are good at - instead, countries seem to race into hyperurbanization and population replacement