Pencil Eyeliners: these can last up to two years as long as you sharpen it each time before you use it. This is just going to keep it clean & germ free.
Liquid & Potted Eyeliners: these can last up to one year provided that they are kept clean & don't go all clumpy & dry out.
Powder Eye Shadows: these last up to two years which is amazing, but they don't really last that long anyway right?
Cream Eye Shadows: these last anywhere between six to twelve months.
Mascara: it's recommend that you keep your mascaras for three months. It's super important due to the risk of serious eye infection. However as soon as your mascara drys out or becomes clumpy, it definitely needs to be thrown out.
Liquid Foundation & Concealers: your liquid foundations & concealers should be kept for anywhere between six to twelve months.
Face Powder, Powder Blush, Powder Bronzers & Contour: these should be thrown out anywhere between six to twelve months.
LIPSTICKS: your lipstick are going to last up to two years which I think is the perfect amount of time to us up your favourite lipstick.
At the end of the day, I think you're going to know when products have gone off. If they smell a bit weird, they're clumpy & just not working like they should be, I think they're are your clear signs that you should be getting rid of it.