I think the “getting of letters” is squadron specific so I’m not sure. I wrote to my DS every day he was in BCT, as I never wanted him to go to the mail room and find nothing. Based on when he answered questions that I posed in my letters and when they were dated, it seemed like he’d get them about 3 days after they should have been in his box. I’m pretty sure he’d go to get mail and have several letters from me, his girlfriend, and others. I didn’t really concern myself too much with it as it was out of my control- I had USPS informed delivery and would be over the moon when I’d see 1-3 letters about every 3-4 days, except for while he was at Jack’s Valley.