I wondered the same after doing a bit more reading around. Mines still bubbling away though it looks like it's just about finished and I'm assured that boiling is unnecessary and can spoil the flavour (though all the recipes I looked at online seem to be split 50-50. Between boiling and not boiling)Just made a gallon following Nellie's recipe.
I used to make wine and beer many years ago and I always added boiling water to the ingredients (without the yeast). The recipes for mead I've looked at elsewhere also suggest boiling the honey and skimming off the scum.
Have I made a mistake by not boiling and presumably killing off wild yeasts?
Yes - by killing the yeast by using sodium metabisulphate (2 powdered Campden tablets followed by stuff called "Sorbistat"). HOWEVER - if bubbling has only virtually stopped, it means either that the yeast has reached its saturation point by virtue of either alcohol or of its ability to use the sugar that was in the must in the first place. A hydrometer will tell you if the specific gravity is below 1000 and tasting or using an alcohol measure will tell you if the wine is at its optimum for drinking. If there isn't 12-13% alcohol or the hydrometer shows a reading above 1000, kill the yeast off as described above or fiddle about to bring the alcohol level up to 12 - 13% by volume by either adding sugar if the specific gravity is below 1000 or adding water to help the yeast restart fermentation to use up the residual sugar to get the reading down below 1000. Even then, safety first, stun and kill the residual yeast too.So insurance policy of corked bottles aside, is there a reliable way to determine for sure that the fermentation has stopped?