Why? They are there to represent their constituents and need to be available to meet with them when they can.
I did call both of my senators' offices yesterday and both offices told me that they don't know yet what their holiday schedules will be, because they're being told to expect to stay through Christmas in DC for one of the Healthcare votes.
So, it may be that you just get a meeting with a staffer. It was Friday afternoon when I called - and one office had me call his "scheduler", but I got her voicemail and left her a message. The other had an online form to request an appointment.
I'm working to gather several GA herpers for us to go in together to speak to our senators. Each of us having an important point that we want to cover and ask them question - are they aware of the bill, what is their understanding of the bill, have they decided yet how they plan to vote? And so on. Thanks to Adam for tips on some of those questions too.