CloudWatch retains metric data as follows:
Data points with a period of less than 60 seconds are available for 3 hours. These data points are high-resolution custom metrics,
Data points with a period of 60 seconds (1 minute) are available for 15 days,
Data points with a period of 300 seconds (5 minute) are available for 63 days, 4) Data points with a metric of 3600 seconds (1 hr) are available for 455 days (15 months). Data points that are initially published with a shorter period are aggregated together for long-term storage.
