Thanks for writing.
Currently, the Control Panel removes all previous versions of a product. This could be changed by opening the TelerikControlPanel.exe.config (by default the Control Panel is installed under C:\Program Files (x86)\Telerik\Control Panel) and changing the following entry:
<add key="KeepPreviousParallelVersions" value="false"/> to
<add key="KeepPreviousParallelVersions" value="true"/>
Please, keep in mind that only versions from different releases could exist in parallel, i.e. if you have 2012.2.607 it will be upgraded to 2012.2.724.
Let me know if any further questions arise.
the Telerik team