Generally, the title of a thesis is valid for 3 years, that is to say, if the title is to be evaluated next year, all papers published within 3 years can be used, which is not contradictory to the time period mentioned above. As long as this paper is unused, it can be counted as evaluation data, and the used one can't be used again, so the earlier the paper topic is prepared, the better. For the problems in paper preparation or writing, you may wish to come to the periodical catalogue network to have a look.