The conclusion that the strong horoscope and a domicile lord of wealth will cause you to be rich and live comfortably when you are old is just the words of comfort.
It is too broad to mean that. This saying is just to please the listener.
The strong horoscope with a domicile planet in conjunction with an ascendant means the longer or older, your horoscope will be stronger. It is only according to the meaning of a domicile.
It does not mean you will be rich when you are older.
The domicile dignity of existing planets or/and a lord of wealth also means that your wealth be steadily stronger when you are older. That is its only meaning, not to live comfortably when you are old.
The strong horoscope with a stronger wealth does not mean living comfortably.
There has not been any planet or any kind of dignity that could mean to live comfortably when you grow old.
Each horoscope is very unique.
A diligent man will still be diligent. No matter how rich he is, he will not be sitting idly. It is quite impossible that he will stop working.
The one who has a powerful Mars and/or it sits on Karma Bhava, he is highly probable to be a workaholic. He would die early if he has to stop working.
The one who has a powerful Saturn (good and related to an ascendant) would be used to a hard work. No matter how rich he is, he would like to work hard or to do a hard work.
He will be richer when he is older. But he could not stop it. He could not sit idly and comfortably.
If they work hard but they are happy, how could we say “grow older, become richer” or “to live comfortably when you are old”?