I am separated, so can't be unbiased here, but when exH and I were looking at this and trying to decide whether to live together as 'friends' or properly separate, I did a lot of reading about impact of divorce at various stages of children's lives, in terms of attachment, development etc.
Some of the things that helped sway us to separate when we did (DS was 8):
The impact of parents' divorcing doesn't stop when children become young adults. You can't have your child go off to university or whatever at 18, and not expect ending the marriage not to have a significant impact on them. They have so much upheaval in those years, I wouldn't want to add to it then by them realising their parents had been pretending for a decade.
You want your marriage to model a good relationship. DS would have seen parents who do not share a bedroom, are not affectionate, don't really touch. That's not great for his understanding of how relationships work.
So you could keep living together, but make it clear to any DC that it's not an "in love" marriage, but while you are still in the same house, the DC might still hold hope, and it could all get a bit confusing. If one of us did meet someone significant a few years down the line, then the separation of homes would have to happen then, which would just be putting of that situation.
I actually think calling quits on a marriage earlier, before it deteriorates utterly into loathing and resentment, might produce better outcomes for many couples. While some marriages can recover from years-long bad patches, from other people's stories as well as my own, it does seem that when the trouble starts, it generally heads in one direction. I think people should be less averse to relationship counselling as soon as issues start; this could help save relationships, but also can help end relationships constructively.