We recently reported several times that the support for the powerful TRIM command was not yet implemented on Mac OS X for SSD. The consequence is a degradation of performance over time. This drop in data transfer speed can be minimized if your SSD support the Garbage Collector as it allows the SSD to recycle cells. To get it activated, you only need to let your computer idle, but without turning it into sleep or hibernate mode, simply leave it inactive. This can prevent performance degradation as we illustrate it below with two SSD installed in a MBP. Both units have never been reformatted nor all data value assigned to 0, they have been used for months now:
On the left, this is the graph generated from the test of an Intel X25-M, and on the right a SSD based on a Indilix Barefoot controller. In both case, writing performance is very similar to the original one, bot to say identical. So the Garbage Collector function does its job, even though the TRIM command would be faster. Last but not least, if this can allow you to wait till Apple finally decide to bring support for TRIM, you should also keep in mind that the GB function is compatible with SSD-based RAID volume, whereas it is not true for the TRIM function.