Every time an event finishes some people will have event tokens left in their backpack. Whether it is because they didn't watch the time and were too late to trade them at the vendor, had trouble logging in or whatever other reason.
That doesn't really matter; people have event tokens left and no way of spending them because the event vendor disappears. But what is so bad about being able to spend candy canes (winter event ends in January) in February? Or spending Doubloons (summer event tokens) in October?
I suggest that the event token vendors stay permanently in Eldevin.
And I think the best way is if they get a building somewhere in EC (plenty of room still) to house them.
During events they always stay at the Eldevin City Central Square, but no need for that if their event isn't up. So a building should do fine.
So far we have 5 events (Winter, Valentines, Easter, Summer and Halloween), and some room on the calender for extra events. So a building that can house around 10 people should do quite well.