Three hours. Even with the help of FAQs I found mostly useless, it took me three hours to finish that last puzzle in Moreau Castle.
And holy crap I unearthed a fatal bug! Thank God I didn't save or I would've had to start the game over from the beginning!
In that last block-pushing part in Moreau Castle, if when the water's drained you push one or two blocks close to the right edge of the rising platform and the other one or two slightly overlapping the edge from the the part where the water will fill in (if the platform rises a little bit of them will be covered), turn the water on, and turn it off again the blocks will stack on top of each other. You will not be able to move them again. The puzzle has no reset option. If you were unlucky enough to run back to the first save point and save after this happened you won't be able to continue with the dungeon and will be screwed forever. I've seen this confirmed on one Japanese site. In other words, if you manage to somehow stack any of the blocks on top of each other in any way other than the one that completes the puzzle DO NOT SAVE YOUR GAME. I almost had a heart attack until I realized I hadn't saved it like that!