Every year I have a photography tradition. With the start of the New Year I start a totally new Lightroom catalog (or library if you like).
In Lightroom you can organize as many photos as you like. You could just make one “mega library” and be done with it. But I have found that it’s easier to find things in smaller libraries, and even easier if you break them up by year.
On my portable Lacie Drive you will find each year labeled, “2010 Complete”, “2011 Complete,” and so on. It’s a simple way to track which library I should be working in for the year. Additionally, I make a copy of each library and put it on my Drobo. When traveling the Drobo stays packed away, but when stationary for a while I ensure that all of my data is backed up to the Drobo. See, at some point I know my portable USB drives will fail, they always do. But with a complete backup to the Drobo as well I’m pretty certain I won’t lose all of my photos.