Given that the RGS was a low budget operation, if it (and #20) had survived as an operating entity to the present day, don't you think they would have dieselized as quickly as they could, or at least built some sort of Goose-like contraption to haul freight trains? If that's the case all RGS steam would have met the torch years ago.
'Tis a far, far better thing that #20 is currently undergoing restoration to operating condition. With careful operation and maintenance, she should last indefinitely for the education and pleasure of future generations.
Ed