I don't mind if the mains choose not to be together, I don't want them to be forced to separate or one or both of them pass away at the end.

Hmm this is hard lol. Maybe The Four (2015). Also Xuan Yuan Sword, more 'bittersweet' than happy but most don't die. And The Classic Mountain and Seas. It's a happy but absurd ending. Well take your pick :P
Ufff well having on count this is really hard to chinese fantasy writers... I could say : Perfect couple (金玉良缘)
Puhh, i don't know if that's the kind of Fantasy you are looking for, but if i remember correctly than "Palace: The Lock Heart Jade" had a happy end :)
The Legend of Qin
The Journey of Flower
the one that no one above mentioned: Love Through a Millennium
Second The Journey of Flower. One of my favs but the ending is a little less than desired but it is happy. Also one of the best second male leads ever. P.S. If you are a fan of Huo Wallace like i was, it will take a while to get used to the dubbing.