I'm now aware of the risk of being classified as backward because I use this Packs for well over 10 years for an indestructible Brown 6550. Although I mainly wet shave and dry shaving against the infamous "five o'clock shadow "before the cocktail hour insets ;-), I feel perfectly shaved. After each change blades / shaving foil my vintage shaved always like new.
The fact that I am completely satisfied with this product, I have under these circumstances probably not stress. As long as the battery remains steadfast, I'm going to buy the 31B continue.