Thanks for your reply. One problem might be that I manually change the source a citation refers to (i.e. I change the tag from, say, "ABC" to "ABCD" so that a different source is displayed). This probably takes up some time because the new source has to be found and inserted.

But also, if I only change the page number of a citation that also takes those 2-3 sec.

I use about 1500 citations in that doc. After I read your post I tested on an empty document..and field updating also took quite long there. My suspicion: it´s not the number of citations used but the number of sources in the current list (ca. 900 in my case).. But I have no idea.

Any further thoughts on this very welcome..but my feeling is that I just have to bite the bullet, right?
Guido