"Normal" frequency of urination?

My husband, aged 60, with stage 6 or 7 AD only goes to the toilet once in the evening. I put him on the toilet in the morning and sometimes he makes a wee but sometimes not. Then he won't go to the toilet again AT ALL until 8.30 at night. He drinks a lot of fluid a day and eats normal meals so how is he keeping in all the urine? He also only has one bowel movement a day, usually at night. Is it harmful? Before he got Alzheimers he emptied his bladder a few times a day.