They never forget some of their hard-core habits, but can no longer perform some of them adequately, even though they still think they can do just fine; ie technical handicrafts, bill paying, driving. My mom also gets agitated if you wont take her out to buy stuff all the time and go to restaurants because that was her life before. Eating and shopping every day. Spent a lot of money. Had a lot of money, used lots of charge cards. She no longer has these. We try to take her out twice a week, but still she gets very upset and disappointed if you won't do certain things to the degree she is used to. I have gotten her over this hump a little bit. She can't remember or learn much anymore other than her habits and also talks constantly about her mom and dad, etc.
The hardcore habits and personality weaknesses become exacerbated and more twisted up when you get old. Drives us nuts sometimes, but I care for her in my home because I think nursing homes charge a lot, CEO's earn a ton, pay the help poorly, etc. and often deliver poor service in skilled nursing section due to lack of good supervision and adequate supplies and help. I was a CNA and worked the nursing homes, so I know.