I know exactly what it's like. My wife was at home with our first son. I couldn't tell her where I was going or how long it would be before I could write again. Sometimes I'd get several letters at once.I wrote so many letters to my ex husband when he was at sea .. that I knew his 8 digit personal service number off by heart... and 45 years later I can still reel it off.... and all the letters were sent to a BFPO address.. which is British Forces Post Office... because clearly when a ship is at sea somewhere in the world.. it can't be delivered to the ship itself by regular methods....
.. so the BFPO office would deliver sacks of mail to the ship about once a week sometimes longer sometimes 2 weeks.... so by the time I'd sent a letter to him.. and he'd received it.. and then sent one in return.. sometimes he sent 2... there could be as long as 3 or 4 weeks between correspondence.. not ideal when the wife is home alone with a baby.. as I was and were so many other Navy wives