When to throw PTR mask out?

[nyshaak]

I have the PTR mask gift set, that I opened a while ago and didn’t use enough. There is no expiration date. I have been storing them in cook place. But when should I Throw out a sparsely used PTR mask? (Pic of the mask set) Peter Thomas Roth Mix, Mask & Hydrate 

 

[SportyGirly125]

@nyshaak There should be a container symbol on the back of the jar or the bottom of the jar that lets you know when you have to throw it away after opened.