One of the ten things that Bodhisattva Samathabhadra says that a person on the Bodhisattva path should do is to request the Buddhas to continuing teaching instead of entering parinirvana. Given that a Buddha is fully compassionate and omniscient, he or she would want to teach if doing so is beneficial to sentient beings and would also be aware whether teaching is indeed beneficial to sentient beings. For example, the historical Shakayumni Buddha wanted to enter parinirvana because some of his sangha was becoming complaent that they would always have the Thus Come One as their teacher. As such, it would seem that a Buddha would be able to decide well the timing of his parinirvana.
Given the above, I wonder how would it is appropriate for one learning to walk on the Bodhisattva path to request the Buddhas to continuing teaching. Is such an action for the benefit of the practioner to generate a wish of englightment and to take refuge in the Buddha? Does a Buddha need to enter parinirvana at a certain time, otherwise it would become harmful to him or herself or to the community at large? Is a Buddha unable to stay longer to teach if practitioners do not make requests? (Sorry that I am unable to phrase a precise question, but I hope I conveyed my gist and my confusion clearly enough.)