While working in 3D Modeling using AutoCAD 2008, after a while when I go to use the views my object shrinks and disappeears.  I am forced to continue using the free orbit tool.  i would appreciate to know what I am doing wrong.  Thanks.

Maybe you are so far away from 0,0,0 that when you change to a different view you lose sight of your objects.  Have you tried repositioning the origin of your UCS?Not sure why you would have to use free orbit to see your objects.