All assessment was done within a one-hour session, so there was little delay between relevant documents. I agree that it is likely that the threshold would be to some degree "reset" if the assessors were to take an extended break in the middle of reviewing. But then you would also have other issues of consistency arising from such a break.

What was the time delay on showing each document on the sequence of showing relevant documents? If you have small delay in showing relevant documents, then I think this effect could be temporarily not permanent. If this is correct then the relevance threshold increase rate is temporarily which is a great observation for web search engine dealing with users. But for assessors, they can come tomorrow and the relevance threshold stay the same as starting point for today. If my understanding is correct, then is there any way that we can say the users can assess K number of documents without effect of assessor threshold flexibility in a specific period of time, say daily?

Thanks, fixed.