This read-only value, bounded 0 to 96, reports the number of previous 15-minute intervals for which valid performance data was collected, capped at 96 (24 hours worth) unless the interface came online within the last 24 hours, in which case it reflects only the intervals since it came online. This tells an admin how much historical performance data is actually available and trustworthy for this DS1 interface, which matters when interpreting the dsx1Interval* history table, since a recently-activated interface won't yet have a full 24-hour history to draw conclusions from. An engineer investigating a DS1's error history who finds dsx1ValidIntervals reporting only 8 would know the interface has been up less than 2 hours and shouldn't expect or rely on a full day of historical trend data.