Language reverts back to default language

I've noticed that after a period of time the language chosen reverts back to the default language. Meaning, if the user chooses Turkish and doesn't click anything for awhile, the subsequent click displays the site in English again.

Is there a way to control this?

See my TEST site.

No, the language code is stored in session, thus will go away after a while, this may be fixed in the next coming version of zen.

I'm also trying to address this version in Simple Seo Url module, I will let you know when a stable version comes out

Regards