I recently heard from a new writer who was frustrated with how long it was taking to hear back from an agent who was initially encouraging about her work. The agent had said that the writer should hear something in 8-10 weeks and now 12 weeks had gone by without a word. The writer wondered if that meant the agent had lost interest.
I explained that, just as there are different time zones across the earth, there are different time zones within publishing. For example, there is agent/editor time (based on weeks). And writer/illustrator time (based on the number of seconds since the manuscript was emailed). The key thing to remember is not to take these differences personally.
Most agents and editors read on their own time, not at work. And while we may say to ourselves, "Well, that manuscript I sent would only take them an hour to read," they have stacks and stacks of manuscripts that would "only" take an hour to read. On the subway home. After the babies are put to bed. While watching their middle kid's swimming practice. Also, those stacks include manuscripts from writers with whom they already have established relationships. And just when the agent or editor is getting to one of those manuscripts, they have to set it aside for a sales meeting or a procurement committee meeting or a design meeting or contract negotiation. . .you get the picture.
On top of these daily meetings, there's the Bologna Book Fair. And ALA. And BEA. Some editors and agents generously share their knowledge and expertise at SCBWI conferences, which takes them away from the office which makes it even harder to get to that "free" time reading.
Whatever you do, don't interpret silence as (a) avid interest (as I used to in the early days; I would think the longer someone kept a manuscript, the more he/she liked it. Not so much. Especially with those early manuscripts.) or (b) complete disinterest. It's more like (c) the agent/editor is tap-dancing as fast as she can.
My advice to the writer who contacted me was to make one of those yummy summer cocktails with an umbrella in it, and take a deep breath. Be assured that agents and editors are really, really nice people. They would like to get back to you sooner than 8 weeks but it will probably be more like 12. Or 14. Or. . .But they will get back to you. And if the wait's too long, there isn't any harm in a courteous note or email inquiring about the status of your manuscript.
Or you could always make another yummy summer cocktail.