The HTML which the RadToolTipManager outputs contains only a DIV element and also the TargetControls IDs are outputted as strings in the controls's $create function. This being said, there is not a significant difference when you use one RadToolTipManager or more on your page - this will not influence the page's performance and will not make an overhead.
Serrin, have you tested the performance when having one and more RadToolTipManagers on a page? If you have noticed performance issues or an overhead, please provide a sample reproduction project along with a detailed explanation and information about the version of the control. Once we receive it, we will research it further.
All the best,
the Telerik team
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