Is it normal for an elderly person to doze and groan in the chair most of the day?

My Dad is also 90 and he sleeps about 18 hours a day. 12 hours at night, then many naps throughout the day.

Dad naps in his bed, also reads there. He does not have a chair that he could nap in. So if he is not at the table on his tablet reading/watching right wing economic news, he is in bed, except for the 1-2 hours a day he leaves the house.