Hello I'm a Lightroom beginner,
I have multiple Aperture Libraries on an EHD, one for each year 2001-2014 (I've already imported 2015&2016). I tally about 317 gb of data for all these photos, I have no idea how many images total that is. I keep seeing in different places there is no upper limit to how many photos you can have in a catalog. Any advice for working w large catalogs?? I am v. organized as it comes to keywords, ratings, collections etc.... Thanks!!
The catalog is just a database. There is no practical limit to the size of a catalog. I think you should consider using keywords as the best way to organize that much data.
Lightroom will tell you how many images are in your catalog, this information appears in several places including just above the filmstrip at the bottom of the screen.
In any event, there is no limit to the number of images in the catalog; one user in this forum reports he has over 600,000 images in his catalog, and it's working just fine.