So what's the difference between Libertarian Communism and Anarcho-Communism?
Either way, you're being extremely vague. Communism is impossible in one country, it must be global, and as such it must be protected. What length of time is enough to suggest a Socialist state has "failed?" What metrics determine AES countries have "failed?" How quickly must they achieve global communism to be a success? These are rhetorical questions, you don't have to answer them all, but they do point out more of your idealism, rather than materialism.
Secondly, and the question I do want an answer to, what method do you believe can succeed in a measurably more successful way? Simply stating Libertarian Communism isn't truly sufficient, as you have already said, Libertarian Communism has never once lasted more than a couple years, in Catalonia, or in Primitive times.