I see your point, what I don't see is the cost of the feature is worth having the feature. You see, everything services does costs something, usually this is in system resrources, be it CPU, RAM disk space or bandwidth.
IF this person spent 10 years with the same nick and it shows in their /ns info that they have been registered for 10 years, then the staff can set the nick to not expire (/ns saset NOEXPIRE on) out of respect for the users loyalty. this will preserve the nick and at the same time not cost any more resources than adding an extra flag to the users account. Which is a better solution all around than your suggestion.
[Edited on 19-12-2006 by katsklaw]