I've said that before! But, you know, it's because the words have two different levels of grr.
But fervid and fervent? I mean, come on. What's the point here? Pick one, dictionary! And just let that one stick!
... And I'd prefer fervent over fervid, if you don't mind, as clearly, this whole issue started with me having to look up fervid on dictionary.com after reading a passage in my work novel.
Plus? It sounds cooler.