Well, I work too, between 10 and 12 hours per day. But I admit my work is flexible enough that 80% of time, i can take a 1 minute break every hour.
My demonstration was in "normal" conditions. But you're absolutely right. A day fighting Dark Lord brings about -35% incomes, and that's around -25% when I fight Edwarda.
Yet, this still make for a lot of moneyAnd I have to admit that so far, i've been lucky enough to have obtained most of the boss event girls in a week or less.