Hi,
The current version of the plugin performs quite well when changing languages or searching for translations. I also have lot of texts in my test scenes and I haven't noticed any lag.
However, there was an issue with the way the terms were displayed in the editor. After a few thousands, it could become impossible slow to scroll the terms list because terms were searched several times in different caches to find out if they were missing from the source, how many time were used, and a few other hints the editor gives you to easy the localization.
But I'm glad to say that this specific issue was fixed in the latest version (2.3) and will be available in the assetstore in the next days along with the Live Google Synchronization feature! General performance was improved quite a bit and browsing/parsing the terms in the editor is now smooth no matter how many terms you have.
However, a workaround to speed the browsing/make searching even faster on the current assetstore version, is to separate your terms in several Language Sources.
Normally, its recommended having all terms in the Global Language Source (I2Languages.prefab) but its also possible to split them and add a few sources to the scene. That way, the source's inspector will only deal with a subset of the terms which makes browsing them easier
(But again, the new version solves all this issues and its just a couple days away
)
Thanks,
Frank