There is no limit to how many times it might update as there is no fixed schedule, in the past I have had as many as 4 in a day on a number of occasions. However, one of those is likely to have been a program update, 4.7.1098. There were only two VPS updates that day so I don't know where you got the other update (or what kind of update that was) from.
avast checks for updates numerous times per day so I don't know if you were confusing a check rather than an actual update.
There were three VPS updates on the 5th though, so I don't know if this might have depending on your time zone appeared to be 4 in a day.