The characteristics of D76 have been studied many times before, over many decades in fact. This particular developer should be standardized upon and used either when first freshly mixed, or about a week later when it has had time to reach equilibrium, which seems to then be stable for maybe six months or so provided its in stock concentration rather than in working dilution, and stored in full glass bottles.
I divvy up the mixed batch into an appropriate number of full tightly sealed little glass bottles with the right volume in each being sufficient for a single development session after its dilution to working strength. I never reuse or try to replenish any developer, although that once was done in big assembly-line style commercial labs needing large daily volumes.
I realize that people bend the rules in various ways, but always, I suspect, with some kind of penalty to quality or predictability being inevitable. When in doubt, carefully test relative to you own intended application.
Polyethylene containers are permeable to oxygen, especially if thin from recycled material. The cheap camera store variety are awful in that respect. Stick with lab-quality glass bottles and well-sealed tops instead.