The idea that going to idle at high altitudes will induce shock cooling
which will eventually trash the engine seems to have a high 'voodoo'
quotient to it.  But there is a very good reason not to descend like a
rock--efficiency.  

To gain that altitude, it took a lot of time, gas and loss of airspeed.
A cruise descent gains back time, gas and airspeed.  A mass at altitude
is stored energy; use it.  Don't fritter it away by chopping power and
dropping into the pattern or approach.  Granted, ATC may not always
cooperate but never hurts to ask.

In smooth air, let Vne set your power.

Chuck Jensen