Never set the Stale Time property in a Tuning Policy shorter than the poll cycle time. Otherwise, points go stale in the course of normal polling. Instead, set the stale timer to be longer than the largest expected poll cycle time. This period can vary depending on how many Px graphics you view.

For each point, the stale timer is measured from the last time the point was updated. For example, if you have a 10-minute stale timer and an 8-minute poll cycle time, you will have some points with values nearly 8 minutes old. If you stop polling, those points go stale roughly 2 minutes after polling has stopped, and not 10 minutes.

This scenario has resulted in some confusion, where the expectation was that after viewing a graphic, any points in it should stay up for the 10 full minutes (or the configured Stale Time) before going stale. However, the actual time depends on how long ago they were last polled.

Special Tuning Notes about the Stale Time Property