Firmware is still faulty, reading old data very slowly

When new, this SSD is very fast plus low energy consumption.
For old data (written more than a month ago) read performance but strong breaks (around 100 MB / s instead of 500 MB / s)!
Samsung has tried to remedy with a new firmware and a Performance Restoration tool this problem but it occurs to me at 2 EVOs on as before. In AnandTech and H one can read that this also occurs in other and Samsung have not really has a solution (as of 2/23/15). Samsung's idea the data repeatedly can rewrite not be really serious, because it takes time for an unnecessary and, secondly, the life of the SSD massively reduced.
Since the reading performance is the most important for the normal user and the data are not continuously rewritten I would advise against this SSD at the moment in any case.
Two stars I forgive, because after all, no data is lost.
From this error, the 840 EVO without being affected. For this, Samsung has also provided no tool.