I would much rather updates were as required, rather than to a schedule.
Not sure if it was my imigination but wern't there two updates today?
I think you'll find that just about every a-v around works to a fairly standard schedule when it's "slow", in terms of new stuff appearing in-the-wild, but updates much more frequently if there's a flood of new viruses. I don't think anyone else can come even close to Kaspersky's "standard", which is several times a day, but that's still their normal schedule.
And yes, we've seen two updates (so far) today -- I've seen 3 a day sometimes when the net is going crazy with new infections, and others who've used avast longer than I have may know of times when there were even more updates in a day than that.
So avast, like every other a-v I know of, updates "on schedule" when that's appropriate -- and as required when
that's more appropriate.
Best,
Mike