I was looking at AVG which you are required to start the update yourself.
I've got AVG 7 (free edition) and have scheduled it to update automatically every evening, which it does (on my ADSL connection) in about 5 seconds, from start to finish. If you are not on line when the schedule is due to run, it will automatically try again when you next connect to the internet. I've used AVG on and off for 5 years now and, although pretty good then, it really has come on in leaps and bounds and must be a real thorn in the side to the likes of Mcaffee and Symantec.