New champions and reworks issue

Good day to you, I wanted to know how long does it take for an incredibly strong pick be nerfed to the point of being actually balanced? It's frustrating that every single new rework and new champion introduced go through patches of being Op that its no fun even playing the game, if not with those champions. I play top lane and Sett is just plain outright OP. if it's not sett, it's newly reworked Mord and that's for top lane only. Please help to understand this cause it actually frustrating me. thanks :)