When taking a lot of timelapses, the Lightroom catalog increases in size. Today I have my "ordinary" images together with the timelapse images in the same catalog. But I´m thinking of splitting it up in separate catalogs, with the timelapseimages in one catalog.  Is there anybody who have done this, and is there a good idea?

I don't think it's a good idea, because you wouldn't be able to edit any stills (from the other catalog) anymore while a time lapse is exporting.