Seriously, I wonder about this.
I've heard several of my older relatives and colleagues say that as they've gotten older, they have become more critical and less tolerant about certain things.
Yet I've read that people tend to mellow out as they get older and don't let the little things bother them so much which would seem to contradict the above.
Maybe it just depends on the person?
If you buy into the functional development theory, as one gets older, they start to tap into using their inferior function more. An IxFP would use Te more, which may make them look more outwardly critical.
I sometimes wonder if health issues contribute to the grouchiness seen in some older people. I do know that certain medications can alter behavior, so that could lead to greater irritability. If you're not physically feeling good, it's easier to become more irritable by things. Also, if you feel lack of control over your health, you might start acting more controlling in other aspects of your life to feel that at least something in your life is in control. I know people who have been hospitalized that are like this. They start complaining about seemingly little things that wouldn't have normally bothered them before. Things like the light being too bright, too much ice in the drink, etc.