How long is a product good for?
Answered[ Edited ]
Generally, there's a symbol on the product itself, or on the box, that tells you how long you can use it after opening. It looks like an open jar, and it has a number with an M with it, like 6M, 12M, etc.
I took a picture of my own MUFE Lift Concealer -- the icon says 12M, so it *should* be good for about a year after opening it. However -- always use your instincts -- if yours is separating or caking, it's time to replace it, no matter what the icon says.