For my kitchen, height for a kitchen's upper cabinet is 4.5 feets (54-inches). This gives me enough working room on counter top with 20 inches of clearance between the two while still allowing easy access to the cabinets for the average height adult.
When I built a house for my mother, who's about 4'-10", I lowered the upper cabinets a couple of inches for her. There's a cathedral ceiling in the room, so no soffits. No one has ever noticed the difference.