No. Strings tend to wear out as much by losing elasticity as by having their surface wear down.
When should you use a double stop on a violin?
By the time a child or an adult can play simple tunes, they are already ready to start playing two notes at the same time - I mean easy double stops, not fingered octaves! Once they are able to play single-note scales with shifts, by definition they are ready to start on double-stop scales.
What are double stops on a violin?
In music, a double stop is the technique of playing two notes simultaneously on a stringed instrument such as a violin, a viola, a cello, or a double bass.