Know when it's time to wave goodbye to your beauty must-haves. It's a sad day when you realise your favourite beauty product is no longer what it used to be - your foundation has become cakey and your lipgloss just doesn't taste as sweet as it used to. Did you think to check how long you've had it for? Because cosmetics and skincare must-haves don't last forever as we explain.

Mascara: Three to six months

This slowly fills up with bacteria the more you use it, as you dip the brush in and out of the tube. If you continue to use your mascara after the recommended time you'll end up with clumpy lashes and, at worst, sore peepers. To make it last, avoid pumping the wand and if it's an expensive product perhaps only use it on special occasions, priming your lashes beforehand.

Moisturiser: Three to 12 months depending on ingredients

Moisturiser lasts for ages, doesn't it? Well if it's an all-natural option than the chances are unlikely, as the ingredients tend to go off quite quickly. Check to see if there's a creation date on the bottle and if it doubt give it a sniff - off products pong. Keep it in a cool place out of direct sunlight to keep it that little bit longer.

Perfume: 18 months to two years

It's not unusual to have around three bottles of fragrance on the go, as you wear what you're in the mood for, right? Just be wary of the alcohol wearing off and changing the chemical balance, giving it an odd smell and colour. To avoid wasting your cash, perhaps stick to purchasing small measurements from now on.

Lipsticks and lip glosses: 18 months to two years

Lipglosses are liquid based, so compared to lippys they won't last as long. Is the colour offish and taste a bit tangy? And do you notice a change in consistency? Then it may be time to bin it, especially if it's one with a wand as they harbour bacteria. Lipsticks can simply dry out and become difficult to apply. Compare your older option to a newer product to see how it should be before smothering it on.

Concealer - 12 to 18 months

Stick concealers are known to last for longer than the liquid pump options, as the pump can get clogged and the fluid inside could end up being contaminated, especially if you use it to cover up spots. Clean the applicator of your pump product regularly and wipe after each use. And, most importantly with all make-up and skincare, don't share! No matter how much your pal is begging to use your YSL Touche Éclat.

Foundation: A year

Liquid foundations are more prone to going lumpy or separating, making them virtually impossible to apply. A funny smell is also a sign that they're not safe to use. Try to go for a foundation which has a pump or dispenser which keeps air out and doesn't let bacteria in. Powder based compacts can be used over a longer period than the fluid options, and as long as you keep your brushes clean and check your sponges often you shouldn't have to worry too much.