For full disclosure I am a self taught home brewer, with fairly low standards of what I consider drinkable. Having said that I do try to get the most out of every brew.
Not sure anyone can say for sure how long a ferment will take. A myriad of factors come into play. Yeast, wort or must, water, temperature and tge stability of the environment.
When the hydrometer drops low enough then it is finished. If it stops bubbling before the hydrometer drops low enough, then one of the factors above is wrong.
Trust your instincts, what's the worst that could happen? Case of the shits if you drink too much of a bad batch and a learning lesson no matter what.
TC