Hahah i don't get the meaning either... Maybe it is just an exercise for you to learn vocab. But If you wanna think about it , maybe it can mean: if you are a good father you will enjoy better your days with your kids... you will always find time to take care of them no matter how tire you arrive home ... you will live longer and happier... that you be my guess :D
My advice is that if you're ever marked wrong for responding "they are X-ing" instead of "They X", you should report it as a problem so it can be added as an alternative. That said, my sense as a native speaker is that "good fathers are having long days" is a fairly unlikely sentence compared to "good fathers have long days."
Who knows? Usually, when people say they've had a long day a lot, they're talking about work.
Are they implying that "good fathers" have to work long days to provide for their family? Why?
Is it because "it's the place of the man to provide"? Would it be as simple as integrated gender roles? Possible...
Is it an echo of the propaganda of a capitalist society, always equating people's self-worth with how much money they are making? Pressing people to work more, putting in long hours in fear of getting fired, of not being able to pay their mortgage and bills and provide comfort for their children. Leveraging this fear to keep people docile...
Is it a bit of both?
Maybe it means "fathers who spend a lot of time with their kids sure find days to be very long". In which case it might be about stay-at-home dads.
It is necessary not to confuse "evolution" with "reforms". Esperanto evolves, like any national language, but it is necessary to establish fundamental rules to prevent everyone from creating their own Esperanto and no one understands each other. Zamenhof, the creator of the language, did not ban reforms, he just advised against them. And, seeing that all the reforms did not bring results, bringing chaos instead, he decided to establish a Scripture, untouchable, that can only or should undergo changes when the international community is about to adopt it. I don't see why "gepatroj" cannot have "gepatro" as a singular, since this does not violate any of the 16 Fundamental Rules of Esperanto Grammar. I see there, a natural evolution of the language.