Hi Ed, as a former Lightroom user I had the same question on my mind. Started with multiple catalogs, one per year, but right now collections are restricted to one catalog and since all my LR organization workflow was based on Collections that would gather images from different years, I had to start from scratch and work on one single catalog hoping that performance would not be significantly affected.
Have not had the time to import all my images yet so I am not sure.
Just wanted to give another point of view in case you use collections as I do.
regards.
Paulo