JohnR's comments are valid across all FR drivers -- there is the huge pressure of product development, and fierce competition in the rapidly evolving FR segment.
If you survey the market, there are few, if any, widely available FR drivers that were available 4-5 years ago, that are still with us today. Even ones with the same model numbers have evolved.
In the case of the FR125 (i hope i'm not stepping out of line Bob), there is another very significant factor. Due to shake-ups in the OEM manufacturer industry in China due to the current economic slump, it is no longer possible to make the FR125.
dave