IME, the biggest predictor for people looking younger than their age is exercising and avoiding alcohol. I'm sure sleep is in there since people who do the other 2 normally also sleep ok.
I'd add tobacco use and UV exposure to that list (anecdotal of course).
Constant stress seems the biggest ager. Intermittent stress (even at high levels), punctuated by periods of relexation, doesn't seem as bad.
See: US presidents before-and-after vs corporate CEOs
Sleep is in there, trust me. I'm 29 and look 40.
i think genes are a bigger factor
I disagree. Genes play a role by setting a min/max kind of like guardrails, but there can be a wide gradient between that min/max. Even people with arguably 'great genes' look terrible if they abuse drugs, alcohol, or their body in other ways.