Relevancy has nothing to do with recency any more. An item can appear first in the relevancy list that was listed 2 months ago, and an item that was listed last week can easily be much lower down even if they have virtually the same tags and titles.
I don't relist items until they expire. In fact, when I list things only half the time have I seen a spike in views and hearts. But this is just my personal preference. I've not tried relisting items before their expiry date, so I can't say for certain if it's still effective with the relevancy changes or not.
It's up to the individual really, but I wouldn't relist. It can get expensive, and if you're not making many sales, you'll end up losing more than you gain.