So you have put a number of X25-E in a RAID array or is this X25-E a single SSD on the SAS controller in AHCI mode?
If its in a RAID array there is nothing much you can do the SSD by its self will wear level and will free up space to write new data but at a slower write speed.
The RAID controller probably presents the the drive as an array to the OS.
Wear leveling is an interal process which the drive determines where to write data. The issue you want to avoid is dirty pages. Without the Toolbox or TRIM, there are few options. There are 3rd party space conslidation and 0 write programs but results are mixed. The sure way is attach the drive to a standard controller and use the Toolbox.
The performance degradation depends greatly on your usage pattern. For a desktop using basic applications, it might be months. For a DB with constant I/O, it might be a days or weeks.