Well the daily incremental updates are in the region of 8-10 a day, but in the 18 years I have been using Avast Free I have seen more than 10 in a day. That way the download size is relatively small, however from the introduction of the Streaming updates that is much smaller so it keeps the main virus definitions very up to date.
Yes a virus definition/signature would first have to be created due to new discoveries, but that would always be the same no matter what way you decide to update the virus definitions. But waiting a week to update would put you potentially further behind the curve.
However, how you decide to proceed on your system is entirely up to you.
I'm not that paranoid either, but I also have plans, based on if you don't want to lose it back it up, making system and data backups on very regular intervals. I guess you must do the same
