As long as there are a few cases in the community-- and there always will be-- the end of each lockdown potentially will trigger a surge of cases, and thus a new lockdown.

I think what is really going on here is world leaders assume China is most knowledgeable about this virus, because goodness knows its labs probably have been studying it for 15 years, they don't have confidence that China is forthcoming about what it knows, and in a few nations globally the effect borders on catastrophic so it's not something to be ignored. So, governments have copied the more knowledgeable actor, which happens to be an autocratic communist government, in hopes that it's approach is the best informed and effective scientifically .

Thus, the answer to 'when do the lockdowns end' really is: when we feel more knowledgeable about the virus than the nations that resorted to placing their populations under house arrest, and therefore feel confident enough to stop following China's example.