That's an impressive running time on one fill of gas - butane?
My manual controlled Millie ran for 63 mins last year on one fill of mixed butane/propane gas pulling one small coach on an end to end layout indoors, requiring running round at each end. Later in the year it put in 2 runs of over 50 mins on my small portable layout, which uses Faller eTrain track (15" radius), at a model railway show.
My radio controlled Millie is still running in, and like wise my 45mm gauge Millie which has just been fitted with new slide valves & the timing adjusted, so they do not run for as long (yet).
Chris Cairns