There is no cut-and-dry answer to this. Some say that when your added ingredients (lemon and ginger) have naturally sunk below the honey – which can take several weeks to a month, others say that it's simply ready when you decide it tastes best. I tend to leave it between 2-4 weeks to ferment before starting to enjoy it. The longer it sits, the more the flavor will develop! I recommend using a wooden spoon to give it a taste at two weeks - if you like it, transfer it to the fridge to slow the ferment. If not, keep at room temperature to further ferment for 1-2 weeks and test again.