You don't have to be in the room as the system is playing. Since you mentioned a harsh sound, I'd stay out too. Run one of your systems about 4-5 hours a day with the cables breaking in, and keep track so you know when you've reached 50 hours.
Some cables really do need this to get to their final sound. Morrow cables, of which I own several, recommend over 400 hours. It's because the cables are made up of many small gauge solid copper wire which is plated(or coated) with silver and each wire is then individually insulated. They can sound pretty gross after 100 hours, then take a long time to reach audio nirvana. Solid copper doesn't take that long.
