Avira servers have reached their limits and it seems the company does not want or cannot invest more money for more bandwidth and traffic.
I would say often or it does not work. "Sometimes" was valid before Sept 2009. In Sept and Oct 2009 happens often.
not only me,,almost everybody https://www.wilderssecurity.com/showthread.php?t=250786&page=2&highlight=avira definitions update if you can take a look in their forum,,you'll see all the complaints.
A while ago I experienced this problem too (had to dl the big ivdf_fusebundle_nt_en.zip - THAT worked fast to my amazement! ) but then I decided to buy premium license (special pricing: 25 months for < 20 EUR) ... and look - if you even can! - how FAST update servers NOW are!! So there clearly is something besides the webfilter you get for your money!
Seldom and actually it doesn't matter if they're a couple of days behind. I can't remember when Avira last time caught anything. I think the most important protection is firewall, updated programs and common sense.
I added this to my list (my Avira has updated once a day....) The update servers of the free version of Avira Antivir are undersized. For this reason the first update may take a long time, even an hour or so. As the install package comes with very old virus definitions, one is not well advised to continue surfing without the update process being finished. One can speed-up the first update by downloading the latest Avira updates here, then double-clicking the Avira system tray icon and choosing Update > Manual update, and searching the downloaded file with the file manager thus opened. You may occasionally meet update problems also in the future, but Avira should update itself on its own approximately once a day.(As Avira has market-leading heuristics, small lags in updates are not as fatal for Avira as for most of its rivals.)
I haven't been able to update for two days now - I'm in UK. I guess it could be just mine. But anyway it did the same with me about a month ago, or so. I might now switch to something else. I am only using Avira on demand so no biggy. Maybe this is a more aggressive approach at manipulating their free users to purchase a license.
I've experienced on-again/off-again updating problems since summer of 2008. For about two-thirds of 2009, Avira updated for me without incident but still, there were several isolated periods of time when updating was a problem. It was sometime around October of last year that the updating problem became (to now) permanently manifest, ranging in severity from a bothersome two + minute delay before the download started to periods of time when I couldn't get signature updates at all. My experience is almost exclusively with the "Classic" (free) version. During the past two years, I did take advantage of six month trial licenses for both Avira Premium AV and Avira Security Suite. While running those trials, updating never seemed to be a problem. As recently as yesterday, the updating problem remained for me. Following the download and installation of the New Avira 10 (beta) Personal AV, the updating process was exactly as with the free version of Avira 9; the update module would report that it was scanning for updates and it was over two minutes before the updates began to download.