Sorry, I don't have any personal experience on this matter, but I can give you an idea about the dual program here at CSU because I have a friend in it now and I work with two people who are in it now.
It is typically seven years (or atleast that is what they try to make it). If your research for the PhD doesn't go well or if you have trouble publishing/ writing a research article for publication it can be longer though. You start off doing research, so you find a lab that you are interested in that can take you on. This is also I believe what determines which PhD program you enter. The gals I work with are all getting theirs in molecular biology. The program looks like this:
Year 1: Graduate courses, laboratory rotations to choose a laboratory, begin dissertation research
Year 2: DVM program Year 1 & graduate electives
Year 3: DVM program Year 2 & graduate electives
Years 4 & 5: Dissertation research, thesis preparation and defense
Year 6 & 7: Final two years of DVM program
I don't know how this differs from other schools. The major benefits with it though are that you can theoretically get your PhD faster than the regular route (but as I said before this isn't always true). You also get a stipend ( I believe) for your vet school years, and get paid during your research years so it is often not as hard on you financially.