Well spotted, Mickeg.
Looking back at the archives ( http://thorncyclesforum.co.uk/index.php?topic=4412.msg28971#msg28971 ), the last reduction in late 2012 was from 2.35 to 2.1 (for riders who weigh under 100kg). The link at Rohloff's site is broken, but I remember checking at the time and based my own 36x17 selection on it.
I recall at the time, Andre figured the hub had sufficient safety margins for even lower gearing than that allowed by Rohloff ( http://thorncyclesforum.co.uk/index.php?topic=4412.msg29001#msg29001 ).
I suspect the link is broken to avoid the embarrassment of the remark in the removed advice that it was positively the last lowering of chainring/sprocket ratio -- and here we have another lowering permission. I forecast at the time that it wasn't the end, and in the correspondence started by my post that Dan references in the URL above, I and others agreed a ratio of about 1.7 as possibly understressed enough even for the cautious Herr Rohloff.
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It is ironic then that after I spent the time to work out what Herr Rohloff knows and wasn't telling us, the circumstance of going over to a midmotor forced me to fit the same 44x16 gearing that Mickeg uses for everyday work. I was a bit worried that I might have to learn a higher cadence than my 45-60rpm mashing, something I've tried and failed to do before, but it turned out I'm stronger now than when I had to go down to 38x16 (and tried to go to 38x17 but the Germans who supplied my bike on Herr Rohloff's orders wouldn't fit the "illegal" components!), the motor is not only torquier but has better software, and I have learned to use both the Rohloff gearbox and the pedelec software better, so that my problem with learning a faster cadence in practice didn't arise. In fact, i'm doing so well on the current 44x16 (remember, gentlemen of experience, though I ride in very hilly country, I have a motor to help on the steepest hills), which is a cheap trial with an optional pressed steel Bafang chainring, that I have decided not to order the projected, very beautifull, billet-machined 42T aftermarket chainring (the smallest that will fit) for the time being.
All the same, when last weekend a lady came by arrangement from upcountry to look at my Kranich and ride it around the supermarket parking lot, and asked which of the offered cranksets she should order, without hesitation I said she should order the 38x16. This is on 29er wheels but applies pretty much to 26in wheels too, especially for tourers. 38x16 still seems to me such a no-brainer for easy everyday work, utility cycling, recreational cycling, weekend camping, and aftermarket component availability, that unless you're an experienced big overload tourer, or you're really decrepit but still have mountains to conquer, it is an automatic choice.
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Dan's put his finger on the decisive factor in determining how low you can gear: balance. I've found on the steepest piece of road I ride on that 5kph/3mph is about the limiting speed for my best cadence of 60rpm because it is not possible to keep balance below that. If I lose the cadence, or slow it, I have to put a foot down, and on a hill steep enough to gear down that low, that means you can't start again. Perhaps the butterflies can use the centrifugal gyro force of their spinning legs keep their balance at a slower speed in unchallenging riding conditions, and thus gear lower, but even for them there must be a natural limit, and by common sense it can't be too far below 5kph.
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I conclude from this that, whatever the reliability limit of the Rohloff may be, it is below the limit rider balance imposes on a practical bicycle. A spot of quick mental arithmetic tells me Herr Rohloff won't ever have to lower the permitted ratio on his gearbox to the 1.7 that Martin and I and others agreed (back in 2012) would still be reliable. I think there might possibly be one more permission relaxation, which even the stumppullers will consider a ratio too low, and that will be it; or perhaps 1.9 will be so obviously far enough, the ball stops rolling.
