It still increase increase a bit (It was 308 per 15 min or something like that, not 325). I expected a larger change, but it's okay.
It's still worth it, for everytime i'm afk for more than 30 min.
I still don't know if I should farm the dark lord (more gold from item selling, possibility to get a new girl) or arena (faster exp, meaning faster lvlup, meaning larger max and stamina refill, meaning faster advance in story, meaning guaranted story girl more quickly, meaning more money). I don't know I don't know