Bifenthrin for Spider Mites - Shelf Life once Mixed?

[realoldbeachbum]

Hello OB - For a year and a half I battled Flat/False Mites. They went through my Bellina collection like wild fire! Thanks to you folks here at OB, I found Bifenthrin. I applied it twice and voila, mites disappeared.

Now almost 9 months later, at the other end of my grow room, I see a few scarred leaves looking VERY much like the same old mite damage. Once again, I will pull out the big guns -- because they worked so well last time.

Here is my question: Does anyone know the shelf life (effectiveness) of Bifenthrin AFTER it has been mixed with water. [Thinking I need to keep a batch handy for the next several months.]

Thanks, ROBB