No, it is not possible to set an idle timeout for UFT 11.5x/12.0x, either from the license server or client sides. This is not enabled via the Sentinel licensing mechanism and cannot be changed.
Reference: https://softwaresupport.softwaregrp.com/doc/KM184108
The only timeout mechanism included with UFT 11.5x/12.0x is if the UFT software crashes on the client. There is then an internal 15 minute clock that will sever ties with the concurrent license token, releasing it back to the license server (but only in this scenario of an ungraceful closure of UFT).
The ability to set an idle timeout is only available with UFT 12.5x and above (AutoPass license mechanism).