If not for the physical aspect of it (better take care of your body now, because it doesn't get easier), my experience of growing old is pretty awesome.
You get cool perks like seniority and respect just because you don't look like a kid anymore. Even though you think it's mostly the same "you" than in your 20s, people, mostly rightly, assume you're wiser and more trustworthy.
That translated, at least to me, into getting more money and less shit for roughly the same amount of work, less need to prove my worth and all in all a chiller life. Money is a lot less an issue than it was before, meaning I don't stress about that much anymore (definitely not the case for everyone, but I would gamble it is for most of the HN crowd). A lot of things that were sources of stress are now under control or in the DGAF category (money, women, career, ...) and I can focus on more interesting parts (family, the meaning of life, everything).
10/10, would grow older again.