I've recently been receiving treatment at the excellent Dermatology Department of University Hospital Plymouth - better known as Derriford.
While chatting to a nurse specialist today, I mentioned Sunscreen, assuring her I always used factor 50. She then reminded me that almost all sunscreens have a shelf life - which she finds many patients are surprised by. She suggested I write the purchase date on any bottle as I buy it, and check it's not expired before use. She showed me several bottles which have a small picture on the rear label, usually with a little '12' inside a bottle. That's the shelf life -in months.
So before setting off to Plakias, check any lotions you pack!
Stay safe!