There's a small translation mistake. Leon says "It takes 2 months for your body to recuperate" and then Rossweise says "I never heard all this about 2 DAYS". Well, this manhua has a lot of them (wich is quite sad) anyways.
I'd say my most pressing worries are:
1) Rossweise will live EASILY 200-300 years more, actually I don't even think she'll age for the next 100 years.
Meanwhile Leon, who's 30 (I don't remember his exact age) realistically won't live another 60 years.
His daughters will be like 7 years old in dragon years when they see him die of old age at this rate.
Not only that, but his increased aging will give away his lies sooner or later. He's already spent 3 years in the silver dragon castle. Sure, 2 of those years he was locked in a room so only Rossweise saw him, but that also means that he's been in the public eye for a whole year now. And sad as it might be, a whole year IS time for a human.
Also, if I remember correctly, the curse Leon gave Rossweise back in chapter 1 makes it so after He dies, SHE'll die too. So that means that, even if Rossweise doesn't age, she'll die with Leon anyways.
I remember also that Rossweise cursed Leon too, but she had modified her curse to be different. Sadly (I partly blame the translation) I don't quite understand the differences between each.
To worsen things off, even Leon didn't know at 100% how the curse worked, since logically he had never used it, nor had seen anyone use it either. So anything could happen.
I'm going to bet for this theory: The curses will somehow feed eachother or end up working in a way that, IF one dies, the other dies too, BUT if NO ONE DIES, then the other doesn't die too. That would mean that Leon's lifespan would be equal to Rossweise. (I think a human mind can't tank 1000 years of memories, but this isn't that kind of story).
I believe also that it has SOMETHING to do with WHATEVER IT IS that's been eating away at Leon's magic for the last THREE YEARS of his life.
Think about it. 3 Years of ALL of Leon's magic. A man that, in good shape, can solo a powerful dragon emperor EASY. That's A LOT of magic, wherever it is now. Maybe it's in his daughthers, maybe in the curses, maybe in Rossweise, maybe nowhere, maybe stored inside of Leon, maybe the traitor that backstabed him has it (Let's remember that we don't even know who that person was, and I don't think even Leon knows, since he was focused on the dragons).
This story is interesting. It's not OH MY GOD SO GOOD, but it IS more complex that you'd believe based solely on it's title and premise of "A hot dragon woman forces dude to fuck like crazy"