Since Q2 2012 the RadToolTipManager offers a new property - EnableDataCaching . It defaults to false to preserve the old behavior - a request is made for the content each time a tooltip is shown, including subsequent showings of the same tooltip.
When EnableDataCaching is set to true caching is enabled and only one request will be performed for each target, regardless of how many times the same tooltip will be shown.
This can be useful in scenarios where the content that is loaded will not change over time, e.g. static details about a product. This allows the initial page load to be quick, because all the data for the tooltips will not be retrieved at this point, yet in the same time prevents excessive requests for the same data which can reduce the server load.
Important: when data caching is enabled only simple HTML content is supported for the tooltips. This means that controls that rely on postbacks and Telerik UI controls cannot be put in the content. There are several reasons for this:
Only the HTML string of the content is preserved (i.e. cached), so all event handlers and ScriptControl instances are going to be lost. The next time this HTML string is shown the styling may appear correctly but the Telerik controls (or any script controls) will not work (e.g. a RadRotator will not rotate even on click of its buttons).
Hover over the same image again to see the difference when data caching is enabled - the timestamp at the top of the tooltip will not change over time.