Makeup does not last forever, and the honest answer to how long yours has left is printed on the carton rather than on a website.

Find the small open jar symbol. It is on the carton of every product, and it has a number and the letter M inside it, like 12M or 24M. That is the period after opening. It means the product is intended to be used within that many months once you first open it, not from the day you bought it.

Two dates, and you use whichever comes first. If a product also carries an expiry date, the usable life is whichever of the two arrives sooner. They do not add together. An unopened product still ages.

Eye products are the exception, and they are the short one. Mascara has the shortest life of anything in your bag, and the widely given guidance is to replace it within a few months of opening rather than when it runs out. The reason is the wand: it goes back into the tube every time, and the tube is dark and damp. Replace it on time even if there is product left.

Never add water, saline or anything else to a drying mascara. It thins the formula and gives whatever is on the wand something to live in. If it has started to drag, it is finished.

Powders last the longest. Blush, bronzer and highlighter are dry formulas, so they keep far longer than anything creamy or liquid. In practice what fails first is the colour and the way the powder picks up on a brush, not anything else. If a powder has developed a hard sheen on the surface, that is product and oil compacted together, and you can scrape the top layer off gently and carry on.

Lashes. Our Magnetic Lashes are made for up to 60 or more uses, and how close you get to that depends mostly on how you take them off and store them. Remove them gently, keep them in their tray rather than loose, and do not put mascara on them.

Tools. Brushes and the Makeup Sponge do not expire, but a sponge is porous and does not last indefinitely once it has been through many washes. Replace a sponge when it stops springing back or will not come clean.

Two things worth doing today. Look at the open jar symbol on your mascara and work out when you opened it. Then check the shade you reach for most and see whether the colour still picks up the way it used to.

If you are unsure about a specific product, email [email protected] with the batch code printed on the carton and we will tell you what we know about it.