Hi,
It is the natural thing that is a consequence of the current workflow.
Just a few comments from my experience:
1. Most of Launchpad Translators Team members never subscribe to this
list.
2. Three days or something less than a week is almost an average term of
participation in the project for an average LP Translators member
(calculation is based on the data about Ukrainian team members).
3. LP lacks any notification system about changes in your favorite
projects. There is no way to configure a mail notification like it is on
Transifex or Pootle.
4. For some reason "Translations you can help complete" list on personal
page does not show your projects or even the projects of Canonical.
5. Sure, you can register some special mailing list for your project
announcements but this can decrease the project visibility and
contradicts with the idea of crowd wiki-style translation on LP.
So it is a normal thing to send the short messages into this list about
your projects as notifications (even once in a 3 days). There is no
other way to contact active translators.
Best regards,
Yuri