Page life expectancy alerts in Icinga

We are receiving frequent page life expectancy alerts from Icinga monitoring. We have plenty of memory allocated to the server. So I would like to know the ideal threshold values to configure in Icinga configuration to get rid of the alerts. My server holds a memory of 512 GB memory.

Icinga Monitoring System Notification
Notification Type: PROBLEM
Service Name: SQL SERVER:MSSQLSERVER - Page Life Expectancy
Service Status: CRITICAL
Service Output: [CRITICAL: Page life expectancy = 620]
Hostname: []

Which plugin are you using to detect the PLE? AFAIK the value depends on the ressources of a MSSQL-server.
This article gives a good overview and a formula to calculate thresholds.