AFT continuously monitors the mortgage market for any changes that may affect prepayments.

The major parameters were last set in the beginning of 1996. Since then, the model fit to the actual prepayment experience has been remarkable. The model did not over-project the low levels of refinancing behavior in 1996-97, it did not under-project the high levels of 1998; and it provided an excellent fit to the 1992-93 refinancing wave.

AFT's OAS-based durations have been comparable to those observed in the mortgage market (as measured against movements in the FNMA commitment rate).

AFT modifies the parameters and the functional form of the model from time to time to better account for the more unusual collateral such as very high premium or low discount originated mortgages.