Silly sod - Varnay didn't sing Isolde in 1953. She only took on Brunnhilde and Ortrud, which is rather like running four consecutive four-minute miles instead of five.
In an hour.
With a knapsack on.
Game girl - not maybe as forbidding as Caruso taking on the tenor lead in Aida, Boheme, Butterfly, Traviata and Tosca within six days at the Met in 1908, but not bad going.