It seems that letters take about 8-10 days so I assume it will take at least 14 days for letters/boxes to get wherever they are going. I know it takes 8-10 days for me to get letters from them once they are postmarked to when they arrive at my house (I've only gotten 2 letters though). However, it depends on their mail system and how far from their "post office" they are, I'm sure. I tend to send letters every 1-2 weeks and boxes once a month (all I can afford or I'd do more, lol). Hope that helps!