The conditioning thing is way overblown. Luka led the NBA in minutes and played till the Finals. Go back and watch Luka lighting up the TWolves and watch him and Antman go at it. Antman looked like he was in the 15th round of a scheduled 12 round fight
Yeah, I don't know anything about his off-season workouts, etc. I know that at 25, he can get away with a lot of stuff that he won't be able to in about 5-7 or so years.
If he adjusts what he does in the off-season as he gets older, he should be fine. If he does like Shaq who liked to "play himself into shape" and never adjusted as he got older, then it'll become an issue.