I don't think that age limits your ability to accomplish your goals, whatever they may be, but it does make a difference in how you get there. I was 25 when DH bought me my first (post-childhood) bike, and I did 14 miles my first ride, and we did an MS 150 the next year with not nearly enough training. I rode for a few years, then stopped when I had my first child. Starting up again this spring at 34 was definitely more challenging. I've been building my mileage up much more slowly. I've also noticed that what I eat for pre-ride fuel and post-ride recovery has become much more significant to my performance levels than it ever was before. Sleep is more of a factor than it was. Simply put, I could do a lot more on a lot less when I was mid-20s than I can at mid-30s. And I'm still young! I can only imagine that the importance of these factors only increases with age.

So my goal now is to keep at it consistently (however challenging it is to find the time to ride with 3 and 5 year olds), because I would hate to have to start from ground zero again in my mid-40s.