I hate to rain on your review unprovoked but some of your conclusions and facts are inaccurate.
The reason why your drive is not performing as it should is obvious, TRIM is not working. When you brought the drive down into steady state you simulated six months to a year of typical writes to the flash (mainstream users).
With TRIM not working the drive never had a chance to recover but many of your other drives did. You mentioned garbage collection as being a problem area for you in the review but SandForce drives do not have a 'normal' idle time garbage collection scheme. Idle time GC only happens when certain perimeters are met, like the drive is XX% full. This is done to reduce write amplification thus increasing product life.
Firmware 5.0.3 is now available from Kingston and 5.0.4 is on the way soon as well. Both fix the TRIM issue. If you contact SanDisk they may send you a drive with the fix. SanDisk just wants to make sure everything is working as it should before releasing it to the public.
You can see how TRIM affects performance over time here:
http://www.tweaktown.com/...e_investigated/index.html
And you can see the SanDisk Extreme 240GB with working TRIM here:
http://www.tweaktown.com/...e_drive_review/index.html
If you want send me an email and I'll assist in getting you the proper assets for a retest. The public release of 503/504 should be really soon though.