What's the magic number when re-drafting?

How many drafts do you have to do before your manuscript will be 'right'?

Should writers really be spending as long polishing their work before submission as some would have us believe? Going through laboriously, line by line, and making our verbs wonderfully strong and emphatic and our metaphors sparkle? Or is this one of the great fallacies perpetuated among new writers?

Perhaps, instead, we should just write that first draft (a difficult enough task for many!) tidy up the spelling and grammar, incorporate the changes suggested by one or two trusted readers and then send it out?

To some extent, the answer depends on the individual, and where they currently are in their journey as a writer, remembering that each of us works differently.
I read a post a little while back originally written back in 2009 by a writer called Dean Wesley Smith, who has written and published under a number of pen names. It raised some interesting ideas about the whole writing/rewriting/redrafting process which are specifically targeted at beginning writers. His post on rewriting is part of a series attacking the so-called 'Sacred Cows of Publishing'.

You can go on over and read what he has to say if you're interested - but in summary, he challenges the idea that endless reworking is a good thing, and he states pretty emphatically that in many cases it's unnecessary and could be a complete waste of your time.

My own experience on this is pretty limited, but I can report that when I met with my agent for the first time, she pretty much confirmed the above ideas. Apparently, if you've achieved the 'dream' and you're on contract to a publisher, particularly for something with continuity issues like a multi-book series, they're likely to want to see stuff as soon as you've written it so they can see where you're heading, and how the work is traveling. That means you'd be sending off bits of polished first-draft. Maybe second. No time for multiple rounds of feedback from your crit partners. No time for agonizing over the perfect metaphor.

Remember here that professional staff editors at publishing houses are specifically paid to help with line editing, continuity editing, and overall structure, and will be going through any manuscript with a fine tooth comb. If any writer actually got everything right first time, all those editors'd be out of a job.

For some of us, the idea of actually sending work out into the world is very intimidating. If you never try, you can never fail. On the other hand, as professional writers are quick to point out, if you never submit anything, it's a dead certainty that you'll never sell anything! Just keep in mind that endless rewriting is (or can be) an insidious form of procrastination.

So for those of you who, like me, are still on the journey to publication, and are perhaps out there sweating over every word and every line, worrying whether your work is good enough to submit yet...take comfort in the fact that the only time you're ever going to have to agonize over your work this much is in the lead-up to getting an agent. After that, if the experts can be trusted, it's a whole new ball game!

Note added 2nd December: I didn't actually mention the way I work - which is very slowly. Unlike some of you out there who work super quickly, my first draft takes me a while, but it's fairly polished. Most of my later drafts are to take into account reader comments and add sections, clarify certain points, weave in a new sub-plot etc.