Knowing when to throw things out


We all know things expire, hence the "expiration date" stamped somewhere on a product, but do we really abide by those guidelines? Expiration dates are set at a very standard point not considering every individual's margin of error. So how do you guys decide when a product should get dumped?

I'm going to list my indicators of a couple of beauty products.


Contact lenses


I usually use the year-long lenses when it comes to circle and color lenses. My eyes are usually dry and barely produces tears so I feel like lenses damage more easily on me.
The moment I feel an uncomfortable scratchy feeling in my eyes (usually happens more on the left eye than the right, sometime around 7-8 months into using lenses), I dispose them.


Foundation


Liquid: When the pump starts to squirt out clumps, when the foundation shows any signs of separation. Other than that, I usually run the full 24 months after opening.
Pressed Powder: When the surface starts smelling weird with darkened wet(?) spots showing.
Cream: When the consistency changes and too much dust particles get caught in the foundation (usually when I hit the middle of the pan).

Eye Shadows

Cream type: When the application starts getting uneven and weirdly cakey.
Pressed Powder: ???? I don't have an indicator :'(

Blushes

Pressed Powder type: When it starts crumbling (almost towards the end of a life cycle)

Concealer
I am usually very bad with throwing out concealer, but ladies, I think concealers should be used excessively and often replaced with new ones.

Mascara
I don't wait the three months. As soon as the mascara turns crumby or flaky, I toss it.
Mascara bases fixers are kept a bit longer, but when the white formula on the wand starts turning dark from mascara, I ruthlessly throw it out.


Do you guys have your own indicators?


* Sorry - this post was finished on the 18th, but I accidentally didn't publish it until the 19th :'( I have no excuse for skipping the previous 2 days, but I will make up for it T^T)