Powder face makeup can last over a year, if there is no shiny buildup on the surface & you have no had any skin irritations during use.
These fall into a more extended category since most of us change our colors as often as the seasons change. With the proper care & clean brushes, these can last up to 2 years.
Mascara & Liquid Eyeliner:
They say you should throw away mascara & liquid eyeliner every 3 months, however I'm one of those that will use it until it starts getting dry or I just get tired of dealing with the fact that I don't like it anymore. The only exception is if you get an eye infection, then you should throw it away immediately.
Powdered eye shadow can usually last up to 2 years, as long as you wash your brushes regularly & don't reuse them after an eye infection. However, some will toss their eye shadow after just 4-6 months. Even though they are similar to other powders, since they are constantly used on the eye, they can pick up bacteria and bring it back to the eye very easily.
Pencil eyeliner can last up to 2 years, if properly stored & sharpened regularly. If you sharpen your pencils before each use, it will help keep them clean, which will allow you to use them longer.
Lipstick/Lip Gloss/Lip Liner:
These can all last up to 2 years. Since they don't contain any water, the risk of them growing bacteria is low. But since they are constantly exposed to the mouth area, replacing them after a year wouldn't be a bad idea, or if you've recently been sick.
Nail polish won't go bad from bacteria, however it wil become thick & clumpy & the pigments will settle at the bottom of the bottle. If you shake it & it remains at the bottom, it's time to toss it.
* While you're at it, toss anything you haven't used in the last year.
If cleaned & stored properly, good brushes can last for years, but when the bristles start to fray & fall out, it's time to replace them.