Poor True!
I get the impression the OP knows exactly how to write multiple 1st and has done it successfully before, but was really just asking how to format it properly...
But the 'how often to switch' issue is an important one, and from the sound of it works differently in the US, which may be worth clarifying to be sure I'm not giving dud information here in my original post on formatting.
To recap: in the UK, you can switch as often as you want, and the reader doesn't seem to have a problem keeping up. The first multiple 1st novels were the epistolaries of the 18th century where letter length can vary from 40 pages to a paragraph, and this still works today. In some ways, the multiple 1st is even more attractive to modern readers because it emulates the form of quick-cutting with which they're culturally most familiar - the grammar of film and television. Of course the voices need to be very distinctive as well as individually engaging, but that just means the book needs to be 'well written'...
Personally (and I should stress that - this is my personal opinion, not a fact quoted by publishers in the industry) I agree with Lady Ice that in the set-up stages one needs to give a 'voice' time to establish itself before cutting away too fast - but after that you can follow whatever the characters and story need, without any concern for bleeding over chapters. In my last book, chapter 1 was told from two POVs, chapter 2 introduced a third, and gradually more and more were added as the book progressed. By the late stages, I was able to really increase pace by upping the cut-rate (just as you do in film), and in one battle sequence was changing POV every other paragraph. For one duel, I split the two opposing POVs so that at one point they finished each other's sentences.
How successful this is I won't know until the reviews come in. All I can say for certainty that it's highly publishable - or at least it is in the UK. Over here, the publishers who are very willing to buy a book in that style include:
Harper Collins
Random House
Orion
Penguin UK
Virago
and Hodder Headline.
These are houses who either bid for my book or published one of Michelle Lovric's.
But I'm getting the impression from other posts here that the US market differs, and doesn't like many breaks at all. Is that the experience of you guys?
Louise