>So for any export to file, like financial export files or logging, it is best to implement a filewriter that adds the strings to a temporary file. Either LLF or STRTOFILE seem to work both at the same speed, but would be interesting to compare those two.

When my logger closes, it appends the current log (which in most versions is always the same file) to the end of the annual log. Why annual? Because there was only one big archive log and it would grow mindlessly big over the years and I didn't notice any slowdown. IOW, doing a strtofile("big.log", filetostr("today.log"),1) was so fast that I never thought to check the file sizes. Typically it would add a few (dozen) kilobytes to a file of hundreds of megabytes.

Strtofile() and filetostr() seem to be just wrappers around LLFF calls.