When using the Timeline control, if control is set up to be in Horizontal mode orientation and you update the datasource dynamically to make it use a 'lazy loading' like approach when loading items when the datasource has been updated, the control will jump to the first panel rather then stay on the panel the user was on.
The Timeline should be able to handle this dynamic update of the datasource and keep the user on the panel they were on especially when there are large amounts of data. Current issue makes it so the user will have to start at the beginning and click to get to the end of the control.
An example of this can be seen using the following demo. If you change the orientation to Horizontal then click to the end of the control's items, and then click the add button in the demo you'll see the control will add the items correctly however jump to the first page in the control.