A new (beta) version is released as soon as it is needed. Mostly because there have been bug fixes taking place.
Read for example the post where I had a problem with Avast and Opera mail. After checking to make sure it wasn't something on my system, they fixed the little bug in ashmailsv (along with some other things I presume) and released 4.5.495. That solved my problem. (and ofcourse for others who are using Opera mail)
vps updates will continue with a rate of 1-2 a week, unless there is a large thread. In which case a new update will be released a.s.a.p.
For the program update it is like I said. When a new program update is released, it will be distributed to the users spread out over a week to reduce the load on the Avast servers. (Can you imaging what will happen if 10.000's of users all want to download the new release at the same time

)
Just keep visiting this board for the latest news.