I'd go alone with everyone else on the single catalog theme to a point. You should set a limit, maybe like you do for your closet. If you haven't worn a piece of clothing for say three years, get rid of it. With images, if I haven't accessed them in five years they go in my inactive archive catalog. It's just too easy (and counterproductive) to get in the habit of keeping stuff we shouldn't.
I do think a LR user is wise to consider the speeds of the drives they keep the catalog and previews on, and the work drive the files are on, with small catalogs they can and probably should be on the same drive. Lightroom works better with a powerful processor, lots of RAM, and speedy drives. I'd buy the fastest highest capacity drives your budget will allow. If your catalog is large I'd consider a separate drive just for the catalog and previews.
When I go to Ivy Bridge later this spring I will be buying an Extended ATX board for the extra PCIe slots. I will use the latest/fastest Revo 256gb for OS/programs, and their 1tb hybrid exclusively for my LR catalog/previews, and either a third Revo or fast SATAIII 256gb for my current work drive. Some would say this is overkill, but I've used this setup on several different workstations and the speed is awesome.