Can't tell you how long either would be. But your eighteen months presumably affected by covid - more recent apps are going more quickly.Can it actually take longer than the 18 months ? Literally feel like giving up is the case, we tick every box on the website and they still deny us, cannot believe i'm even in this position of having to appeal.
If other aspects of your app are straightforward, a new app may be quicker (married removes any judgment about being technically eligible).
Of course I have no info about your app or why your cohabitation info was not considered correct.