Dear (insert name),
Really you shouldn’t have bothered replying, certainly not after so long. I know you think you are doing the decent thing rather than keeping me hanging on. But I can assure you I have not exactly been waiting with bated breath all that time; I’d given up on any response months ago – ten weeks is about the limit. Life goes on, so many other things to get depressed or just irritated over. There is always the anxiety phase for about two months after a query submission, checking the inbox with squinted eyes, or only at a time when I can think I might handle it best (though there is never really a good time, but it should generally be on a week night). And then out of the blue in pops your email. Just as well I wasn’t having a good day anyway because that would have certainly spoiled it. Yes, your words were polite, measured, even well-wishing, and your reasons for not replying sooner perfectly understandable. But it comes across as sugaring a bitter pill. After such a long time it is doubly disappointing to get nothing better than what could be the same letter sent to the many others but with my name inserted.
I guess it feels better to get that query in-tray cleared.
So please, any other literary agents, don’t bother replying. Unless of course you are interested in my work.
You are welcome to comment here though.