Lava Loop/Rotary question

I ran across my copy of "Rio Grande Narrow Gauge-The Final Years, Alamosa to Chama, today, and of course had to break to check it out once again.
There are some shots showing the Lava Loop, and in fact a cool shot of the last time it was used on April 23, 1968.
In the book it is mentioned that the loop was to facilitate turning rotary trains. I had heard this before, but was wondering how often this would be used. I guess the reason for my question is this. Would it not be more likely for the Rotary train from Chama, to go into Antonito to turn, as they could resupply there?
I would think trains turning would run the risk of running out of coal, and maybe food supplies should they get into long days of fighting snow before getting back to Chama.
Comments?
Greg Scholl