If you notice that FME processing time is spent writing to temporary FFS (FME Feature Store) files, the issue isn’t one of actual processing time, but how that time is reported in the log file. FME doesn’t log the time taken by each function – often it just reports 0.0. This may be because the time is less than 0.1 seconds (the precision allowed for), or because the individual function cannot be accurately measured. Therefore, the time used accumulates without being reported.
Therefore, when the "Storing features…" process logs the time taken, it reports all accumulated time, giving the impression that much of the FME process is accounted for by writing FFS files.
In the following example, it doesn't mean that 0.3 seconds were spent writing to FFS, just that 0.3 seconds have been used since the last occasion this number was reported:
2010-08-12 10:25:01| 1.1| 0.1|INFORM|Opened DBF File <xxxx> for output
2010-08-12 10:25:01| 1.2| 0.0|INFORM|Opened Shape File <xxxx> for output
2010-08-12 10:25:01| 1.2| 0.0|INFORM|Opened DBF File <xxxx> for output
2010-08-12 10:25:01| 1.5| 0.3|STATS |Storing features to FME feature store file