QUESTION:
After the mission for the MGS is over and you have recieved the
information you need, will you use the MGS in the future?  How long
can you use it for? 

ANSWER from Cheik Diarra on November 20, 1996:  
At the conclusion of the primary mission of the Mars Global Surveyor, 
which will last 1 Martian year (687 days), we will use MGS for at least 
three more years as relay satellite to relay data from landers on the 
surface of Mars to Earth.  I believe we still will have propellant on 
board after that extended mission and could continue using it should 
funding for extended operation be available.

ANSWER from the Internet:
http://mgs-www.jpl.nasa.gov/overvu/mplan/mplan.html
After MGS finishes its mission in late January 2000, the spacecraft 
will function as a communications satellite to relay data back to 
Earth from surface landers launched as part of future Mars missions.