My usage of cosmetics is quite slow as I am the only person using most of them along with the fact that I switch products depending on my mood.
My Acure face wash ended up staying in my bathroom for quite a while, maybe a year till I realised that the original smell had changed. I do not think the product went bad per se but the original smell was missing. I feel that this is a result of it staying too long in a extremely hot and humid climate (where everything gets spoilt or get fungus eventually – including bags, jeans etc.). I am now trying to finish it up.
Also, a lot of my lip balms started smelling rancid and I them away. The chemical lip balm I bought 3 years ago is still good. Hmph.
On the other hand, face washes, creams from brands like Nivea aren’t affected by this climate and seem unchanged after years.
My recommendation is to buy organic/clean cosmetics as per usage basis as they seem to have slightly shorter shelf life compared to the mainstream ones especially if you are in a hot and humid climate.
That is expected considering that there are lesser preservatives/chemicals used. They may however last longer in continental climates.