I'd suggest you don't let the chain go too slack.
If you also get a seized link, the chain may manage to fall off the Rohloff sprocket. I know: it happened to us. At well over 20 mph. By the time I'd bought the tandem to rest, the chain had done some damage to the lovely black coating on the hub. DOH. Next time I clean the bike I'll have to touch it up with black paint.
Also, especially on the tandem I suspect, but it might apply to solo riding too, a lot of slack in the chain can manifest in backlash when out of the saddle.