The current RU:8080 runs started in February 2012 (although there had been similar malware spam URLs before that). A timeline of the dates of the runs I spotted can be found here.
The spam runs always happen on a weekday, not a weekend. Mondays are slightly less common than the other weekdays. Usually there are no more than 4 or 5 days between runs.. but the RU:8080 gang has shut down for longer.
For example, in April 2012 they shut down for up to 46 days, in July 2012 it was 21 days, August 2012 was 31 days, December 2012 for 13 days and February 2013 for 10 days.
Of note the April 2012 shutdown coincided roughly with start of Orthodox Easter, the December 2012 shutdown was from the period between the Western and Orthodox Christmas. The summer shutdowns could simply be because the RU:8080 gang were on holiday (they don't work weekends, after all).
Show a brief shutdown doesn't mean a permanent shutdown. But if it lasts for longer than a month then it's a different matter..
Updated 22/5/13: and now it has been over a month without a peep..