Personal planets in 9th
Mercury/Venus/Mars Can be some of: studying foreign languages, a deep curiosity for foreign cultures, dates/marries a foreigner/person from different faith, with an emphasis on this house it then becomes expecting periods of time abroad, older astrology say these people often die living abroad (not fatalistic just old age, when the time comes), the eternal students, those who keep studying higher education (3rd as you know primary education, 9th is higher), study of languages/law/international things/religion, strong religious faith which is important in the their life. Mars here often gets very sporty, athletic types.
I've Venus in the middle of the 9th and more than half of this is true. Mercury is at the end of my 9th conjunct MC. I've studied about 6/7 languages in full time education, dated more foreigners than nationals, doing a thesis on law and have benefited from legal procedings, have a degree in international business and languages, lived, studied and worked abroad. (plenty of good astrologers on here that dwarf my international experience, but I fit my 9th well). My asc is Cancer so the houses fit your client quite a bit.
Dark Side Planets
I have never heard of effects being later in life...I'm surprised! I've only heard that the end of the current house plays out at the start of life and eventually all events proceed into the next house.