MJP, the first round is small, so it doesn't take much time at all. The last round is the most time consuming, if you do a nice round that size. What can eat up most of your time can be trying to figure out what you will do to continue the quilt. If you think too long, you're out of time. Or you could procrastinate because you think you have plenty of time, and then when it slips away you are left wondering what happened. And don't forget the post office is going to eat up at least one of your weeks. So you actually end up with about 3 weeks to decide what to do and then do it.
Give it a try! Everyone should have at least one RR quilt under their belt!