Should the suction line be cold?

On split system installations, the suction line should be pitched towards the compressor at least

Suction line should be insulated for 2 reasons: 1) so it does not drip condensation everywhere it passes through the homes interior space. ie attic, inside walls etc. 2) cool suction gas is what cools the compressor motor during operation, insulating the pipe carrying it helps prevent that gas from picking up heat from the surrounding air ensuring it remains an effective coolant for the motor. The original reply was also correct, an effort to pitch the suction line towards the compressor should be madr wherever possible to aid in oil return.