Gauge conditions for long-term numerical black hole evolutions without   excision
  Numerical relativity has faced the problem that standard 3+1 simulations of black hole spacetimes without singularity excision and with singularity avoiding lapse and vanishing shift fail after an evolution time of around 30-40M due to the so-called slice stretching. We discuss lapse and shift conditions for the non-excision case that effectively cure slice stretching and allow run times of 1000M and more. 
Miguel Alcubierre, Bernd Bruegmann, Peter Diener, Michael Koppitz,   Denis Pollney, Edward Seidel and Ryoji Takahashi