When I do this:

<xsl:value-of select="format-time(current-time(), '[f][s]')" />

20.000 times in one transformation, it takes around 120 seconds on my
computer, but all the "seeds" are the same!

There are probably a good explanation...

Is there any way a can produce seeds on the run fast enough, or do I
really have to take a day of making a long list of seeds I can pick
from randomly (!) in order to feed the process?

Cheers,
Jesper