I'm in my 30s and one of the big things I've noticed recently is that hangovers are way worse than they were in my 20s. I think I've noticed it especially because I quit drinking for about 4 years or so and when I came back to it I noticed it seemed much worse than my early 20s. These days I'll have like 3 or 4 beers and start feeling hung over before I even go to bed. On the plus side it has really helped me moderate my drinking, cuz I sure don't feel like feeling like shit before I'm even done drinking and for most of the next day!

Most of the other stuff I hear ("Your metabolism slows way down!!!" "Your body starts falling apart!!!") seems to me to be mostly because people stop exercising and eat like shit. You do slow down but taking care of your body can really reduce the losses. I'm a cyclist and ride with guys in their 60s who are probably fitter than a lot of 20 and 30 year olds that I work with.