Originally Posted by Tenhou

Thanks to events you will eventually be filled up with 20 5* characters anyways with full equipment slots and skill level. This is why it's so important to combine the gacha 4*, 5* and 6* because otherwise they can't compete with the event girls in the long run.

Well, for the 6* girls , if you happen to get a double very early in your career, then there's something to say to *not* combine them at first, level one normally, but level the other to 30 not evolved (relatively cheap to do), and only combine her when your other girls start outperforming her.