Pretty much all the publishers want exclusive holding rights to MSs even if they hate them and don't want to publish them - for the standard 16 week wait period you're not allowed to send your work off to anybody else. So after seven 16 week periods, that's already more than two year's worth of wait time for the one MS.
I'm not saying that I am an impatient ass - I know that it takes ages for even the most successful authors to hear back from publishers, I'm just saying that if I were to apply for a job (any job), I would go on a job search site, find the ads that I like and then just apply to all of them. That's all the sending off of the manuscript is, it's a job application - nothing more, nothing less.
Authors are not Gods and neither are publishers - Why are we allowed multiple job application submissions to competing companies in any other industry, but not for publishing? What makes them so special that they won't even follow standard hiring procedures of the job market?
PS: I haven't actually started on the submission process yet - I've just been reading about it & the reading depresses me (re: MS submissions etiquette).
A job application has nothing whatsoever in common with a book submission.
And, look, there's nothing standard about sixteen weeks. It may take sixteen days, or it may take ten months,
But you're automatically assuming you're book is going to be rejected over and over and over. If this is the case, just how do you think simultaneous submissions will help? With simultaneous submissions, you won't even have teh chance to improve your book between rejections, and this is bad.
And pubishers damned sure will reject a simulataneous submission if they don't want them, and they find out you've done this. Publishers have good reason for not wanting simultaneous submissions, just as agents have good reason for wanting an exclusive, and you're just screwing yourself if you don't follow teh guidelines.
Simultaneous submissions are wonderful, if what you're after is a big bunch of rejections in record time. They're horrible if what you really want is to find a good publisher for your book.
Stop worrying about time, and start worrying about what really matters. . .the quality of your book, which does away with the need for simultaneous submissions, and the thought that you're waiting for anything.
Instead of waiting sixteen weeks, you spend the time writing. Sixteen weeks is enough time to have a second novel well under way. Those two years you mention should be enough time to have two more finished books in the submission process.
Trust me on this, when an editor says no simulotaneous submissions, he means it. And, for that matter, when an agent demands an exclusive, she means it. Go against either, and you aren't shortening the waiting process, you aren't improving your chances, your just risking a big self-screwing for no good reason.