Let me ask you this... where are your files stored? Your RAWS and your lrcats. If you said the same place, I'm about to blow your mind. When you create your new LR Catalog, you'll be tempted to house it in the same place as your RAWS (probably your external hard drive), right? Don't do it. IT'S A TRAP!!!!!!!!
When you're editing in the catalog, it'll pull data from the RAWs and bog down your RAM. If you have a Macbook, you might notice it sounds like a jetliner trying to take off. "But Tyssa, I use Smart Previews so it won't use the RAWS!"
You totally should use Smart Previews BUT if you're still allowing the catalog to access the RAWS, it will! (LR is like a 3 year old wanting the raw cookie dough. Unless you take it away completely, it WILL get its hands on it). You should do this: Cull your images Drag your RAWs to your external hard drive Create the catalog Save the lrcat to your desktop or other folder on your computer ("but..." hold on) Import the images creating Smart Previews Eject the hard drive EDIT!!!! By doing this, your lrcat is forced to use the Smart Previews and keeps your system running fast! You'll have to plug in your hard drive to export (so don't forget that!)
I also make a backup copy of the lrcat and save it to my external hard drive (*** but when I edit, I use the desktop one without the external hard drive plugged in- if I make changes, I'll overwrite the backuplrcat)