A traditional publisher will tell you expect a year or more unless your book is in answer to a topic that is current in the news. They have an editorial schedule to follow and your book will be put at the end of the line behind established authors.
The exceptions are for manuscripts that deal with the legacy of someone famous that just died such as Michael Jackson or a topic such as insider trading when a celebrity like Martha Stewart is accused of the crime. A seasonal book can be delayed until the next year; a fiction book can be released at any time. You will only get bumped to the front of the line if you deal with a topic that is all over the news and the publicists can get you tons of media time if the book is released immediately.
The publisher needs to give their in-house editors and support staff time to go over your work with a fine-tooth comb and eliminate any typos and inconsistencies. Part of the year lead-time could be spent with you, the author, rewriting a chapter or two that aren’t smooth. Authors need to have patience when dealing with top publishers. They will work very hard to make your book the very best is can possibly be. They know what they are doing so let them have time to do their jobs.
If you are told you could see your book in print in a week or as soon as a couple of months you have probably found an “author mill”. The companies who will spit out a book that fast don’t care about the quality of each book but rather the quantity of books they can publish each month. This is a poor sign for best-seller hopefuls and sometimes make-a-buck authors. If you are a posterity writer, this may be acceptable depending on the answers to the other questions.