I will be 29 when I start my MS. I graduated undergrad when I was 22 and took time off. Played in a band for a while, worked some crappy jobs, some corporate type jobs, had a kid, changed my career path, spent a lot of time in rivers and woods, got married, went back to school and there you go. Hopefully I will be 31 when I start a PhD. It was a lot of fun and I appreciate it much, much more than I did the first time around. Coming out of high school and going through undergrad always felt like I was jumping through hoops. So it's nice to be on track. My original goal was to be done with everything by the time I was 30, but stuff happens. I have a friend who started his PhD at 20. He's incredibly intelligent, but I wonder about some real world sense sometimes. He'll be OK though.