Short answer: No, the wife of an old fellow cannot demand a divorce.
Sources and/or details
You are only quoting half the requirements - occupation. Health also plays a role. See Shulchan Aruch, Even HaEzer סימן עו - חיוב עונה for the full details.
א: עוֹנָתָהּ כֵּיצַד, כָּל אִישׁ חַיָּב בְּעוֹנָה כְּפִי כֹּחוֹ וּכְפִי מְלַאכְתּוֹ. וְהַטַּיָּלִים, עוֹנָתָם בְּכָל לַיְלָה
Conjugal rights: Each person's obligation depends on his health and his occupation. E.g. הַטַּיָּלִים - healthy, wealthy people who have nothing much to do all day except stroll around leisurely - their wives deserve their conjugal rights nightly.
My translation of הַטַּיָּלִים is per the באר היטב who clarifies as per the טור:
לילה. היינו אדם בטל שאין לו מלאכה והוא ברי' ומעונג ואינו פורע מס ואינו הולך בדרך
In other words, your first sentence should read: a wife has a conjugal rights depending on the health and occupation of the husband.