I usually finish at least 3-4 lippies a year - I guess I could dig the rest out with a lipbrush when I get down to the metal rim but I lack the motivation to do that. I like applying from the tube. I just finished Kinda Sexy a couple of weeks ago and I don't have much left of my Oh, Oh, Oh. I go through several lipglass or CSGs as well. I've finished four or five this year. I don't typically fuss with the rest of my makeup during the day, but I reapply lip products every couple of hours.
I don't usually back products up but I do have a few things put aside: 3 Forever Marilyn powders (just hit pan on my second - first thing I've ever bought a ton of), and one each of Glamourdaze, Apres Chic and Oh, Oh, Oh. I often have backups of basic items I use all the time ahead of me; I have a Mineralize Concealer, a new Moisturetint and a Blotting Power set aside. Those are staples and when I finish one, I pick up the next replacement on my next US business trip. They're cheaper that way.