This is correct. Looking at the most recent FAA CVR reg. revision in 2008, which increased the required duration to 2 hours:

"Revisions to Cockpit Voice Recorder and Digital Flight Data Recorder Regulations" [1]

The FAA proposed that all CVRs be able to retain the last two hours of cockpit audio. Both the NTSB and the Transportation Safety Board of Canada noted that the short duration of available cockpit audio hindered the investigation of several accidents.

The Air Line Pilots Association (ALPA) did not support the proposal to increase CVR recording time because the FAA did not propose any increase in the privacy protections regarding the access and use of information recorded on a CVR. The ALPA stated that existing protections are inadequate despite years of its attempts to change the standard.

[1] http://www.gpo.gov/fdsys/pkg/FR-2008-03-07/pdf/E8-3949.pdf