Reading the novel makes me realise having a harem isn't that fun
Depends on your Stamina.
There are men, who can't even handle doing it once a week. And there are some who can easily do it multiple times a day.
It all depends on the individual. Plus, like any physical activity, if you do it regularly in a steady manner, your stamina for it would also increase
(key point, in "steady manner").
Well, in case of this series, the issue isn't even really about Stamina, because MC as a Human is actually on the stronger side when it comes to Stamina.
But he still can't compete with the Stamina of Non-Human races, who are naturally more stronger than Humans.
In the Novel, it's mentioned that Slyphy and Melty are beasts when it comes to Stamina.
While Ira has average Stamina, but she uses potions to boost it.
As for the Harpies, they also have normal Stamina, but they always come in group. Because of their culture developed from being a female-only race with a somewhat shorter lifespan compared to Humans (they have the culture of "community husband", were all the Harpies within the community share one Husband).
