My parents have had separate living quarters in the same house for going on 30 years. Despite his numerous affairs (most were prior to the "separation"), they have forgone getting a divorce due to:
1) cost and otherwise forced division of assets, on his behalf
2) religion, on her behalf
3) much cheaper cost of living for both
4) just less hassle in general (according to both)
5) more than just a bit of nostalgia, as they build the house together in their 20's and I don't thing neither want to give it up.
They do share laundry room, although each does his/her own laundry. The walk-out basement (his quarters) contains a full kitchen, dining room, living room, full bath, laundry room and two bedrooms (that's where we lived when I was little until we could afford to build the main floor). Her quarters contains the same as the basement, although the layout is exact opposite and it has another bedroom in place of the laundry room. There is a double-lock door in the stairway that separates the two.
Occasionally one will ask the other if they need anything from the store if going and are cordial when in the same room together (if it's not for more than a couple of hours), but basically they live their own lives, ignoring each other for the most part. So I guess it can work for some people.