I ferment on the cool end of the yeast range. I have had some that finished in a couple of days and a couple that bubbled for 14 days or more. I primary for about 3 weeks then bottle.
I have also done similar recipes with the same yeast and had very different fermentations. Some need a blow off tube and others have very little krausen.
IMO the yeast are going to do what they want regardless of what you want them to do. The object is to give the yeast the best conditions that you can.
To know if the beer is finished you HAVE to take gravity readings. Although, if I am doing an average beer, get a usual type of fermentation, I sometimes just take a final reading while bottling. I've been lucky so far, no stalled fermentations of bottle bombs.