Milestoning duplicate tickets?

Some of us are clashing on Trac: in one corner, those who keep duplicate tickets and/or set them to appropriate milestones; in the other corner, those (read, only me, I think) who take them out of milestones when encountering them. The way I see it, if the ticket is a duplicate of an "original" one, and said original is already properly milestoned, then what's the benefit of also having the duplicate in the same milestone? And if said original is *not* properly milestoned, then it should be ;-) But that's of course only one side of the ring. What does the other side have to say about it? Regards,... -jmpp