IMO:
If...after ~25 years...this ArmorAll product's
dimethylpolysiloxane-fluid emulsion still has:
• A viscosity of ~300-400 centistokes;
• A particle size of less than 1/2 micron;
• A specific gravity of: 0.99...@77°F;
• A pH of 8.5; And:
• A milky-white appearance...
(with no visible, grungy "floaties"

)...
Then:
It's probably going to be OK to use as it was intended.
Note:
•Knowing the proper application methods for this product is paramount to its success as a: rubber and polymer...(multi-material)...preservative.
•Hopefully you know what the application methods are, and plan to implement them accordingly.
______________________________________________
Bob