Q: Would you ever lay 4″ boards in one room (small office and small kitchen) and 5″ boards in another room (dining/living room) of the same material (Santos mahogany)? We would use thresholds to separate the rooms.
A: Sure. I (personally) can’t think of a good reason not to do so. Good idea to separate the rooms by a threshold in my opinion. Some people prefer to have all the hardwood flow seamlessly from room to room. The drawback with that is if one area needs attention you can’t separate it from all the other areas. When using thresholds you can.