(edited by international telecommuting translator li)
Experience has proven that when you live in a country where the everyday language is not your native one, even after a relatively short period of time (6 months or so), you lose the edge off your mother tongue. This is because languages are constantly evolving with a surprising number of new words and phrases coming into and out of use. For promotional material translations, it is very important that the language used is the current version otherwise, the wrong messages can be conveyed. Only those translators who live in the country where their mother tongue is the main spoken language should be used therefore.