As long as it doesn't freeze, the shelf life is nearly indefinite.
I'm using some old DG, so there'e no reason to bring up the clogging! I know what that's all about.
If you have some 4lb flowable, shake it up thoroughly before you measure & mix. That will place the solids back into suspension. I made the DG work by measuring, filling, then shaking my back-pack like a fool. The I strapped it on quickly, & got about pumping & spraying immediattley. Any pause in starting will allow the settling occur.
The 4lb Flowable that you have goes down at 12.8 oz at the heaviest rate. Settling isn't nearly as bad with this formulation as the DG.
A good tank sprayer is still about a thousand percent better though.