If TRIM is disabled you may see write performance degrade as the SSD is used.
MAC operating systems 10.10.3 and older versions disable TRIM by default.
In MAC OS Yosemite(10.10.4) and above you can enable TRIM by opening "terminal app" and enter command "sudo trimforce enable", then enter "y" when asked do you wish to proceed, enter "y" for reboot notification and your MAC will automatically reboot when complete. SanDisk SSD with Trim command support maintains the performance at an optimal level (as fresh out of the box) over its lifetime and reduces the wear and tear of the drive, as it reclaims the occupied garbage space in advanced, avoiding unnecessary read-modify-write operations. In addition, the wear-and-tear on the SSD is also reduced significantly, as the SSD can effectively manage all the reclaimed spaces. Since a memory block must be erased before it can be re-programmed, TRIM improves performance by pro-actively erasing blocks containing invalid ( garbage) data, allowing the SSD to write new data without first having to perform a time-consuming erase command.
The Trim command enables an Operating System to inform an SSD which blocks of data are no longer considered to be in use and can be reclaimed internally by the SSD to ensure that later write operations perform at full speed.
SanDisk SSDs offer TRIM command support, which is enabled by default in Windows 7 and above, designed to maintain the performance of SSD at an optimal level over the lifetime of the drive.