I found that we can only view the Log report for the last one month.    Currently,  the retain policy of the data is "RAW data for every poll (based on your configured check frequency) will be stored Only for the last one month". 

While “Audit Logs” and “Alert Logs” can be shown the data from the  day of monitor creation(or one year).  Do you consider to show 1 year for “Log Report” and add it to your product roadmap?   Retainment of the Log Report only  for the last one month seems too short.