H1-B stamping and returning to US after a year

[fundoocode]

Hi,
I am going to India in Jan 2008. My H1-B visa is valid till Oct 2009.
I will do the stamping within a month of my India visit.

My questions:
1) Is there any time frame i need to return to US after the stamping? or I can return anytime by Oct 2009.
2) What documents should I ask from my current employer so that I will not have any problem in the immigration if I come after a long break from India?

Thanks in advance...