Jim, Matt, my experience with the 'glider is limited to a shortened season of riding in 2014, and about 3000 kms, all with a new Raven and a new chain.
When I checked my chain last autumn, it was 15 mms beyond Thorn's maximum recommended play of 60 mm as shown in the "Thorn Bikes Owners Manual, p. 9, "Adjusting eccentric bottom brackets". (Note: I didn't measure the play in the chain when I took delivery of the bike in late April last year, so i can't say how much the new chain stretched over the season.) I adjusted the EBB to bring the play below the 40 mm lower mark recommended in the manual.
By the simpler method of checking the play midway between the two sprockets, it's now about 15 mm at the tight spot (happily, the tight spot isn't very pronounced.)
The 'glider does a good job, I reckon, of keeping the chain on the sprockets where it belongs. Most on my kms were done on tarmac roads, with the usual frost-heave jounces on Canajan roads, but for the most part, me, the bike, and the chain were not subjected to serious shocks or bounces.
I'd say that checking the chain's tension when you change the Rohloff's oil should do the trick--annually or every 5000 kms or so.