"Fleeting" - in that another more permanent and more powerful monopoly supersedes them, such as Wordstar, then Wordperfect, then Word. Eventually the roulette ball comes to rest, particularly if the laws that countervail market power aren't enforced.
The roulette ball is still moving. Word is getting hammered by lightweight, online, mobile-available, collaboration-first tools, such as Google Docs and Quip.
