The Qin Dynasty did not survive its founder, but the subsequent Han Dynasty ruled all of China for 400 years.
The Qin Dynasty did not survive its founder, but the subsequent Han Dynasty ruled all of China in 400 years.
The Qin Dynasty did not survive its founder, but the subsequent Han Dynasty ruled all of China for 400 years.
The Qin Dynasty did not survive its founder, but the subsequent Han Dynasty ruled all of China in 400 years.
The idiom "for years" denotes the duration, which is appropriate here. The idiom "in years" denotes the length of an absence. If something were true 50 years ago, then not true for 50 years, then it could be true for the first time "in 50 years". This idiom is used for a long absence coming to an end, which is not the case here.