I read in some forums that brand new timing belts have a run-in (break-in, wear-in, etc!) period of about 2000 kms (1200 miles) when they are first installed on the car. It was said that you should not rev your engine more than 3000 RPM in the first 1200 miles to let the belt run in properly. Is this really true? I ask this because I recently replaced my timing belt and revved my engine to about 4000 RPM (once or twice) before reaching 1200 miles! Did I damage the belt?
If this is a standard replacement timing belt (OEM or direct replacement), there's no such break-in period. You replace and go.
As an aside, there are specific break-in periods/schedules for the engine or cam(s). Taking a cursory glance around the internet, I'm seeing a lot of stuff for breaking in these (yah, that's internet wisdom going on there, too), but everything I'm seeing about timing belts agrees with me stating there is no break-in period for them. I'm not sure where you're getting your information from, but I'd highly suggest you stay away from said forum, because they really don't know what they're talking about (IMHO).