Didn't your mother always tell you to remember your manners?
Well, why not say a simple thankyou? HUNDREDS of letters arrived at each field country office every week, and the translators have to work through them all.
Some translators get paid per letter, so it doesn't matter if the letter is 3 lines or 3 pages long! They may work through 40 letters each, per day. It's not a easy task. Many words need to be found in the dictionary or 'Googled' to find their real meaning. Many translators pride themselves in being as accurate with the translation as possible.
Why not consider putting a small card in with your next letter, addressed to the translator, just to say 'Thankyou' and that you appreciate their hard work? A little recognition goes a long way.
These cute cards are from Pepperpot Stationary, $12.99 for 10 cards