It is advised that you toss out your make up after about 12 months I think. I wouldn't wait too much longer than that. By the time it changes texture, consistency, colour and smell, it is probably way too late. I wouldn't be continuing to put it on my skin/ lips. Chemicals can change over time, so who knows what it would do to our delicate skin.
I wore some liquid makeup from an old little tube, years ago. We gone to visit them, via a 3 hours train trip. By the time we arrived I had a very bad rash on my face! They took me to their Dr, & he suggested I use a moisturiser for sensitive skin. I throw out the tube of makeup when we arrived home, & never got around to opening the $16 container of the cream, which is still sitting on a shelve in the en-suite!
In my experience, powder makeup lasts longer than cream and liquid. Some last up to 2 years without any strange smell, but then I can't bring myself to use them after that. I used to change mascara every 3-6 months to avoid bacteria, but I don't use them anymore since that's quite costly if one considers how many products I need to purchase. Still, I use organics cosmetics, so that can't apply to everyone else.