Hi I'm the integration captain (one step below captain, in charge of programming and electrical) on team 2537. I'll answer each of your questions for my team.
1) This is our teams fifth year and we are planning to build a second robot for the first time this year (if funding permits). I think having a second robot would do amazing things for our driving ability and for keeping all the new mechanical hands busy. But, I think it's a much more secondary thing. If you have build season already under control go for it!
2) We usually plan on meeting on 4 weekdays for 4 hours each and on Saturday for around 6 hours. After a couple weeks (when we're behind) we start working every day.
3) All members are expected to go to almost all of our meetings unless they have a good excuse. A few years ago we took attendance before and after dinner because it was considered in driver applications but we don't do that anymore. If you do split up meetings you probably should have whole subgroups there at the same time.
4) Because of county rules we can't work during the week of midterms so that leaves us 5 weeks. We try to have the design completed by the end of week 1, prototypes and drive train done by the end of week 2, and the robot completed with a week left for integration and driving. Before we start design we make everyone read the whole rule book and have a group discussion about strategy. Last year we didn't compete in a scrimmage but we did send a couple people to scout out the competition.
As long as you have a dedicated team with clear goals you can be successful. There are lots of different definitions of that.