I am wondering about at what point it is okay and not impatient to give up on an agent assessing your work if you haven't heard from them. I have had a submission (chapters 1-3, synopsis, etc) being assessed by an agent since October 2006. In January they asked for the full manuscript. It was sent to a reader, who really liked it but was not sure if it was right for the young adult market. Instead of sending it back to me, they sent it to a second reader, which I was happy about, but due to their backlog they still hadn't got back to me - and it had been almost 10 months - so I rang them and politely said if they haven't decided I would like to send it to other agents/publishers as well. They said it's still with the second reader who hasn't read it yet due to their backlog, but if I want an answer at this point, they'd have to say no. Did I do the wrong thing by getting impatient and indicating I was going to send it out more widely? I had thought that most people do send submissions out to lots of agents/publishers, but in my case, as my manuscript was being assessed by a well-respected agent, I had been advised by the ASA to hold off on sending it to other agencies, until I heard back from this first big-name agent. Did I wreck my chances or generally speaking if they haven't signed me up after 10 months it's unlikely they were going to?
Short answer: If the agency you send it to didn't ask for an exclusive, you didn't do the wrong thing by calling and saying you were sending it to others. Ten months is not necessarily a long time for a full manuscript, but it sounds like they have already said 'no' so hopefully you have already sent it to others ...
Long answer: Each agent seems to have a different policy about whether authors should submit to multiple agents/publishers at the same time. I always expect that authors will submit to more people than just me, precisely because it does take so long to read submissions and make decisions, particularly for first novels, particularly in a genre like YA, in which there are a lot of very good, published authors still writing great work. I'm not sure why the ASA has that policy - and that's just their policy, obviously: you should always check with the agents you send it to. Because I don't ask for exclusivity, I don't like being told by authors that I'm the only one who has it and I should therefore hurry up and make a decision - the reason I don't ask for exclusives is so I don't have those sorts of time pressures, and also because I don't think it's fair on writers.
The conundrum for agents is this: we read and assess prospective clients' manuscripts on our own time, because we don't charge a fee for this (and nor should we). The agency to whom you sent your manuscript bore the cost of the first reader and the second, if it's gone that far, and they may then decide they can't take it on - but they've still paid for that reading time. Because the cost of reading new manuscripts may or may not ultimately bear fruit, it has to be rationed and considered carefully. This agency has obviously taken a while to consider your manuscript, and it's probably because it's been in a queue - most agents in this country have more reading than they can handle, and that's just from their existing clients. It could also be because sometimes manuscripts get mislaid - most of us would have huge stacks of paper around our desks, and things do get lost. And then, sometimes, the agent may end up weeping atop one of those stacks of paper because she has no idea how she's ever going to get through her reading ... At this point, I'm glad this blog is anonymous :)