Quote Originally Posted by mgb74 View Post
FWIW, this hasn't been my experience. I have a bottle opened for about a year with no issues.
Here's what happened:

Plus-X- 35mm.
Fresh film.
Processed as I normally do.
HC-110 concentrate had been open about 6 months and was a dark brown color.
I mixed the developer from concentrate.
The image on the film was extremely faint, including the edge markings.

I assumed that the developer had gone bad, and I threw it out.