Updates are a necessary evil. When you first install any anti-virus program, it will only catch the virus known as of the date the CD was manufactured. When you do update any anti-virus program, you only will catch those known as of that date.
Norton updates their virus definitions once a week, on Wednesdays, more often, if necessary. You have to keep ahead of the bad guys!
You can go their web site and manually download the updates a few times a week. I check just about every day.