There are a number of factors that we must not ignore when treating Rev. 20:10. For one thing, its quite possible that torment in Rev. 20:10 does not mean literal torture (the infliction of physical or mental pain). It could either refer to imprisonment or denote a subjection to punitive measures (Matt. 18:34). It is the figurative imprisonment or testing of the Devil and his cohorts that could occur both day and night. Furthermore, if the beast and the false prophet are not sentient beings per se but representative of symbolic entities, then it makes no sense to speak of their torment anymore than someone might speak about tormenting death and hell in a literal sense (Rev. 20:14-15).
Robert W. Wall points out that Revelation's description of the two witnesses could very well be symbolic of the church's faithful testimony in the face of its enemies (Wall, Revelation, 145ff). The terminology "two witnesses" might be an example of synecdoche; therefore, the imagery could aptly represent the faithful (anointed) conquerors who overcome the wild beast by means of their faith. Notice that the prophets (witnesses) dress in sackcloth, are described as having powers akin to Moses and Elijah, they are killed and their dead bodies remain unburied for three and a half days as those on the earth exult (temporarily) over their unjust death. In view of the overall literary features of Revelation and the context of Rev. 11:10, I suggest that the two witnesses symbolically depict some kind of Christian testimony reminiscent of the ancient Jewish prophets.