Unless I get my maths way wrong, this gives them 3 years to do 15 missions. That's 5 missions a year.... Am I the only one who wonders if they can really pull it off?

The Shuttle is due to be retired in September 2010, so it's a bit more than three years. Despite the recent delay, there are still four planned flights this year. And only 13 flights are needed to finish building the ISS. The last two flights will be talking supplies and heavy spares. Desirable, but not essential.

It's a busy schedule, but doable.