Using Sysdate with a snapshot, will it create problems?

The oracle documenetation on snapshots states that we should not use context sensitive data like sysdate in the defining snapshot query. But my problem is that i can't do a fast refresh (because I need info from several tables) yet I want to get only the updates(~ 100 at night) rather than compete info (3.4 million records). I need to tell the snapshot to get records where the changedate = sysdate to get those days changes. It there any way to do that without creating problems? I am confused as to why documentation states it is a bad idea to do that. Received on Fri Nov 20 1998 - 10:48:03 CST