For many years, or as long as I have sent email as correspondence rather than plan-making or advice-requiring, I used to end my messages by saying something to the effect of "Do please write whenever you have the time and the inclination." I kept this practice up until one of my correspondents shamed me out of it, as it presupposes a reply will not be forthcoming otherwise.
You, dear reader, can imagine my surprise when I picked up J.D. Salinger's "For Esmé--With Love and Squalor" for the first time in well over a decade and saw Esmé ended her letter to the narrator/G.I. this way: "Please write as soon as you have the time and inclination."
Whether I first used it in an email as a forgotten memory from my past, or I selected on that phrase on my own, I couldn't say; but either way, the convergence was shocking.