At Amarok we have usually very short string freezes, or sometimes no string freeze at all. This is because the development team wants to be able fix or correct strings for as long as possible. This doesn't mean that there are actually a lot string changes before a release, but you should check the status of your translation while string freeze is active. A usual string freeze takes about 4 days, this depends a lot on when the Amarok team decides to do a release.
When to be finished
We use to release new versions on Sundays (mostly between 7pm and 11pm UTC), therefore you should ensure that your latest translation is committed before 6pm on release days.
After first release of a new series (x.y.0), translation happens in trunk till development of new series starts (gets announced), then stable translation happens in stable branch till new series gets first release (x.y.0), then translation again happens in trunk. The following drawing might show it in a easier understandable way: Trunk Path: trunk/l10n/LANGUAECODE/messages/extragear-multimedia
Stable Path: branches/stable/l10n/LANGUAECODE/messages/extragear-multimedia
As you probably want to be up-to-date, the translation want it to be as well, so keep your translation up-to-date. The common release cycle of Amarok is about 4 weeks, it is a good idea to take a look at the translation, 3 weeks after last release, so you only have to do minimal adoptions before the release and don't get stressed.
Since releases get announced at the kde-i18n-doc list, we recommend you to subscribe to this list, or ask someone who is subscribed to forward you informations concerning Amarok. Note that this is the only way to get informed about upcoming releases.