The whole premise of manually flying the final part of the approach, in my opinion and experience, is to 'ingrain' that sight picture into your head and train memory muscle for the time that the approach aids aren't available to you.
Most modern aircraft fly an ILS better than I can anyway, I do fly fully manual approaches when I can, just to try and prevent skills atrophy. Again though that is my personal preference and not something that I would try and force upon my flying colleagues. If there is a coded waypoint to 50ft above the threshold then the FD's will give you good guidance and can be left on. If the MAP is behind you the FD's will feed you rubbish and 'AP out FD's off' is the call.
By all means glance at the FD's, if they are giving you good info, during the final approach but the primary guidance factor should be transferred to outside of the cockpit once 'visual' has been called. Those are the skills that we get paid higher than average wages to train and retain for the , god forbid, one time we might really have to rely upon them.