I can't tell you how many times you've asked this question, as though there's some universal timer, and when it dings you have the right to storm in and demand an answer.
See below for a sample: (I think one of you sent this three times with different wording, or you are all obsessed with editors on maternity leave).
My question is, if you're agented, how long should you wait on editors before you decide your agent isn't effective (barring editor maternity leaves, shake-ups, etc.). Two months? Six? Nine?A year?
It's about time and numbers - pure and simple.
For editors, if you are a genre author, there are a finite number of editors who can buy your kind of work (say 8 for the 8 paperback houses). They have at least 12, if not 24 or 36 books they are responsible for a year. Many of those slots are taken up by authors under contract, so when those books come in, they have to drop what they are doing and edit them, because those authors under contract are waiting by the mailbox for their delivery and acceptance checks. Sometimes they make editorial changes, and then they have to read the manuscript again. They have to squeeze reading a new manuscript into their workload. (If you are unagented, you are at the very bottom of the pile).
If you are agented, the editor will want to get back to your agent within a reasonable amount of time, so that s/he will continue to submit to that editor. You should start to get some feedback from your agent three months after submission, if she's done a simultaneous submission, which she would have. However, if your submission was sent out between Thanksgiving and New Year's, or during the summer months, four or five months is a reasonable amount of time. For a full manuscript, you might not get a full set of responses for up to a year, and then, sometimes, it can take even longer than that.
As long as your agent is in contact with you, and your work is on submission, you shouldn't worry. You should know of other authors s/he is repping and whether or not s/he is making sales for them and if s/he is, you know she's working in the field.
It is very hard to get an agent (because there are so many people writing today), so if you have one, you shouldn't just throw her/him away. I have had a few authors approach me saying, "my agent sent my book to 12 editors and was unable to sell it, but maybe you can sell it?" No, it's been seen by the major players and there's nowhere else to go. It's not your agent, it's that book. If I was interested in you, I'd want to see the next book.
Sometimes it really takes a long time. I have one book that took me 16 years to sell (rejected by over 50 editors) but that's a whole post in itelf.
I hate it when my clients ask me who I sent the manuscript to because they don't know the business or the houses or who recently bought a big ghost brothel book at one house, which is why I can't send their ghost brothel book there now. If I'm spending a lot of time updating them, then I'm not selling or reading or editing or brainstorming.
I know you're insecure and anxious, but that's not your agent's job. That's what writer's groups are for.