Go for it! I'm only a year younger than you am just finishing my first year. I also feel you need a little 'life experience' to start a PhD, as you can manage your time better. I see some younger students running around every day, coming in weekends etc whereas I can happily do my work in the day and have the weekends to relax a little. (Older students tend to have more of a personal life going on, mortgages etc!)