Long Power Cord Runs

Currently, I use long speaker cables and shorter runs of ICs and power cord. After asking around, I have decided to relocate my power amp closer to my speakers in advance of a speaker-cable upgrade. The distance from both preamp and a/c power outlet will require around 20 feet of both ICs and a power cord. Does anyone know of any reason why I should not do this? I am not worried about the IC run, since I will use high quality ICs that are well shielded. But I rarely see power cords this long (I will probably have it custom made), so I am concerned that there may be a reason for this. Anyone ever have any trouble using a very long power cord? TIA.