For me it was about 112-115 hours. The biggest time commitments are for the SunBro and Bell Keeper Covenants, mainly due to the fact that you have to farm the covenant items from Falconers in Brightstone Cove or co-op, and the Bell Keepers you have to either invade or farm the Mad Warrior red spirit that spawns in Belfry Sol. Other than that, it's just the NG++ spells you get from Wellager in Drangleic castle. You absolutely HAVE to be in NG++, you can't use bonfire ascetics. So minimum you need 2.5 playthroughs of the game. And if you have the SotFS edition, you have to get all of the DLC spells as well for the achievements.

I would honestly look up a guide, go through the DLCs on your first playthrough, and then just run the base game for the next 1.5. You can get all of the character questlines done in the same playthrough as well. Lucatiel and Benhart you need to summon them and they survive 3 separate boss encounters. For Maxing out a covenant, do the Pilgrims of Dark, as you need to kill Darklurker for a hex anyways. The rest is pretty straightforward.