Although the water cooling system is designed to continue to circulate coolant by convection after you switch off the engine and so continue to cool the turbo, there are several sensible precautions that will prolong the (expensive) turbo's life:
Use a high quality fully synthetic oil of the recommended grade & change oil & filter regularly.
Flush the engine at each oil change, to clean out carbon/sludge/varnish build-up.
Don't rev the engine on start-up, allow several seconds for oil to circulate & reach the turbo shaft before revving the engine. Once you are driving, it is best to wait until the engine temperature is up to normal before using very high revs.
Always allow the engine to settle at idle speed before switching off the ignition, otherwise the turbo will still be spinning fast after the oil has ceased to circulate & lubricate it*.
After a high speed run where the turbo has been spinning at high speed for a prolonged period, allow the engine to tick over for a couple of minutes before swithcing off the ignition. This will help to dissipate heat away from the hot turbo via the engine coolant and oil.
So yes, "resting" the turbo is one of several actions that you should consider.
Hope this helps.
*With acknowledgement to Tech, who a while back explained the bit about the oil pump stopping before the turbo stops spinning if you don't allow the engine to settle!