I ran a clean install to Ubuntu 12.04 and so far everything has been working well.
I especially commend the Ubuntu team for this release.
I only noticed that the size of repository update is now about ~13MB.
The answer shouldn't be followed since the use case doesn't exist anymore.
It's only here as historical value, and should be viewed as such.
It might be useful as experience for the same problem in the future, but the answer may not be accurate.
files are being marked as modified twice an hour, even though they contain the same content. As they hold entries for each package in main and universe this is causing the average download to be very large.
This causes the server to send huge package file again even though nothing has actually changed.
The package file contains the version number and description of the most current version of each package in the repository.
The actual release files contain the date and time of the last real change.
chilicuil has kindly filed a bug report for this and at this writing this is thought to be a problem with Ubuntu archive mirroring mechanisms. The bug is at Note that this bug has been closed, so the following circumvention should no longer be needed or used: Since the affected repositories are the unchanging distribution repositories, one approach to circumventing this problem is to run the following commands immediately before running .
Be sure to adjust them for the name of the archive site you use as well as the name of the release you are using. This seems to be the common refrain, but "sustained activity" can't explain why people have been experiencing this issue on Mint 11 and 12, 11.10 in addition to 12.04 (Note I've always had these large fetches since early alpha of 12.04).
Not everyone will need all four commands--see the comments at the end of the commands. Now that the problem has been fixed, it may make sense to consider how to further reduce bandwidth when running apt-get if you run it regularly and have either a slow or an expensive Internet connection. Ubuntu 12.04 has just been released and thus there is a sustained activity in releasing improvements and bug fixes. Please take a look at the links given in comments elsewhere on this question. With regard to what is perhaps a triviality, I'd like to reward @chilicuil somehow, but as he has not posted an answer and yours is the most informative answer, I think I'll reward you the bounty.
Basically, the issue is this: people using apt-get update several times a day find large 10-20MB fetches. I'm beginning to think a bug report is the correct response here. Try go to your Update manager and remove some ppa's. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).