Evaporation of charged black holes near extremality
  The AdS_2\timesS^2 geometry of near-extremal Reissner-Nordstrom black holes can be described by an effective solvable model which allows to follow analytically the evaporation process including the backreaction. We find that an infinite amount of time is required for the black hole to decay to extremality. 
A. Fabbri, D. J. Navarro and J. Navarro-Salas