...And here is one most significant ones I saw for non-acute CRPS patients that fMichael had quoted at the prior link just above:

The reported duration of limb pain was 4.3±3.1 years...

An Open-label Pilot Trial of Ibandronate for Complex Regional Pain Syndrome, Breuer B, Pappagallo M, Ongseng, Chen CI, Goldfarb R, Clin J Pain. 2008;24:685-689