In order to set the delay,you need to set the ItemRequestTimeout property of the ComboBox .I found this forum has discussed the similar scenario when using Load on Demand.
I use this property, but an empty div appears after pressing a key in the input field. Then, after a time ItemRequestTimeout this div is filled with data
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Kalina
Telerik team
answered on 08 Dec 2010, 10:57 AM
Hello Denis,
I am afraid that currently opening the dropdown with a delay is not supported.
Please, accept our apologies for any inconvenience caused by this.