I have been using jsFiddle to assist in helping answer questions around Stack Overflow, and some of the old code/scripts have started disappearing - seems like it expires af
According to the developer (via twitter tweet 1 & tweet 2):
Until beta, all fiddles are stored permanently. And, currently, they live forever.
See complains about availability of JS Fiddle at:
https://meta.stackexchange.com/questions/149890/prevent-posts-with-links-to-jsfiddle-and-no-code
Today my weekly old fiddles are dead (from question Align to right "left triangle" in menu element).
Any service have maintenance cost. So you can't have any guarantee unless you make agreement with service provider.