I agree with thepoppet - it really depends on the discipline and country. Some disciplines tend to have more students who go directly from college than others. Time to graduate varies greatly by the country and whether a Master's is required or not or whether it's something you earn on the way to a PhD. I'd like to also note that there is also variation depending on which school you attend - I find that some schools tend to attract more direct from college folks while others tend to be attended by people who have a few years of work experience first. Also, some schools tend tend to graduate students earlier than others.
Regardless, even though some programs may lean one way or another, I think you'll find students of all ages in a PhD program. Also, I find that a few years difference isn't really noticeable among students, although differences in maturity definitely is. I say as long as you're interested in the subject, go for it!
Regardless, even though some programs may lean one way or another, I think you'll find students of all ages in a PhD program. Also, I find that a few years difference isn't really noticeable among students, although differences in maturity definitely is. I say as long as you're interested in the subject, go for it!