Are there still good reasons to "preconditioning" your SSD, especially before doing benchmark? And if so, why? Today we have better SSDs and almost all system-configurations support TRIM.
The answer is yes. The professional way of benchmarking an SSD is described.
Before a benchmark is done, if not brand new, the SSD has to be purged to put it into a state that is as close as possible to fresh out of the box. This is usually done by a manufacturer utility that can TRIM/erase the whole disk.
The second step is to apply a workload repeatedly to the SSD, while monitoring its performance, until performance results get into stable state where the repetitions don’t fluctuate by too much.
When the SSD is in a stable condition, the benchmark should be run immediately, not giving time to the firmware to do any garbage collection that will affect future results.