Coax lines have a dominant mode with zero cut-off frequency and theoretically if the coaxial cable is good quality, and its impedance is the same as the source and load impedances at its ends, the cable do not affect the connected circuits and its length is meaningless. Only the insertion loss will change with the length.
Sometime, if the source or load impedance are different than the coax impedance, in this situation the coax length should be multiples of 1/2 wavelength to improve VSWR.
On the other hand, the length of the coax cable should be lower as possible as the system permits, to prevent greater insertion loss.