So, if you'll forgive me:
Please, please, please don't tell me, after I've had your manuscript a month, that you've given me an exclusive (without telling me) and that, because I haven't gotten back to you yet, I'm putting your writing career on hold. I didn't ask for an exclusive (if anything, I advise against granting them, even if they're asked for), so don't say that you'd really appreciate an answer, you know, ahead of schedule, because you've given me said exclusive.
Here are some reasons exclusives are unwise, even if an agent asks for one:
- You'll never have the ability to put yourself in the very best position an unagented writer can hope for: having one offer and several agents who haven't gotten back to you yet. In that case, you can tell the other agents of said offer, ask for an answer within a week, and sit back and see if any of the agent you thought were out of your reach call you up with a plan for your manuscript.
- You'll never get to hear different agents' ideas for your work. Often one agent will come up with something you never thought of--and even if you don't end up going with him/her, this is often valuable advice.
- You'll go with an agent based on what has been written about them, versus what they say. Unless you're using the Jeff Herman and Google and know someone who knows the agent, you're not getting anywhere close to a complete picture. How will you know what it's like to work with that agent?
- You'll never get a chance to ask questions on your end--your relationship, therefore, is one of imbalanced power. Could you ask these questions (How do you see my work? Where will you send it? What is your editing process like? How often can I expect to hear from you? What's your Author-Agent Agreement like?) anyway--and should you? Yes. But most writers don't. You'll feel better about your working relationship long-term
- If you tell an agent they have an exclusive--especially if they didn't ask for one--that agent will either 1) take their sweet time getting back to you because there's no worry of another agent taking the work away, or 2) feel guilty and want to get you an answer as quickly as possible--which, sometimes, means saying No the moment anything goes awry in the manuscript, rather than taking time to think about if it could work.
- Many exclusives assume that if, at the end of the exclusive period, that agent offers representation--that you'll automatically accept. Worse, if you sent out your work without intending to offer an exclusive to anyone, but an agent asks--it's like applying to college normally, and then having one college say that, actually, they'd rather you apply Early Decision. Good planning? GK thinks not.