The mail from Tripadvisor also confirmed that the promo from last year (500 mi/3 reviews, up to 6 per month) is indeed extended until monday (even if the website does no longer state anything about it and the FAQ still show the deadline of Dec 31st). As the miles will only be credited for reviews that are *approved* before the deadline, you should write your reviews today to make sure they'll count for the higher promo value (I wrote mine yesterday, approval usually takes 2 days).