The distance between A/C units in a split system will not affect the efficiency of the unit unless the length is over 100 feet. Copper line sizes are compensated for distance. Split A/C systems are designed and factory charged for up to 50' of copper lines between units. When the copper line sizes are increased for a run over a 50' Freon would need to be added. If the line size was not increased for a distance over 50' then efficiency would suffer.
Ductless splits are the exception, 35 feet max, anything over that distance would affect efficiency.
