Consistency maintenance is a kernel problem in Collaborative Virtual Environment (CVE) research. The approaches used in Networked Virtual Environments (e.g., DR algorithm) could not be used in CVEs, for they could not prevent short-term inconsistency. Therefore, local-lag mechanism has been proposed to eliminate short-term inconsistency in CVEs. Choosing a proper lag value is a key problem in local-lag mechanism. This paper studied the effects of lag value (0ms-900ms) on task performance in a desktop CVE system. Experimental results indicate that the effect of lag value on task performance is not linear. The effect could be separated into four segments by three dividing points: 150ms, 300ms and 600ms. Lag has no effect on task performance while ranging from 0ms to 150ms. From 150ms to 300ms, lag slightly affects task performance. Lag deteriorates task performance seriously while ranging from 300ms to 600ms. When lag is longer than 600ms, the task cannot be accomplished sometimes.