I think they have faction-based or event-long milestones in some of the published event books that tend to work that way. Usually, they tend to tie those in with special resources for the event that can be unlocked with a little XP expenditure after hitting the 10 XP trigger on the relevant Milestone. Getting a new or upgraded power set, or unlocking a new character to play as or a resource that lasts for the entire length of the event, that sort of thing.<br/><br/>I don't think I'd mind too much if you'd prefer to make it a set of free-floating XP bounties, though. It should be a good way to get some decent sums of XP on-hand to unlock those special resources I mentioned. ^^