They don't appear to be useful sizes for general plumbing applications such as taps etc. In any case, I'd suggest that taps are usually fitted (though not invariably) with the best type of rubber washer for the job. A harder washer might not seal as well or might lead to premature wear of the valve seat/thread etc. The Victorian principle of the weak link is that the part most prone to failure should be cheap and easy to replace and I think it best that the washer be the weak link.
Even in my own house where my labour is free and the tools are on hand, I generally strip, descale, and inspect taps every 5 years. I inspect the wahsers. They rarely need replacing and even though I have them on hand I do not, consequently, always replace them. The main point of this is that I live in a hard water area and this prevents the mechanisms from getting stiff and the tap and body getting seized to the point that dismantling cannot be carried out without cosmetic damage.
Given that washers usually last at least 10 years (there are exceptions, particularly if your family has the bad habit of overtightening the taps - possibly a learnt response to having had taps at some part in their lives that were in poor condition and thus tended to drip otherwise?), I'm not sure what the advantage vs possible pitfalls is in having a washer that lasts longer than 10 years, since the remaining maintenance is still desirable.
