If your only concern is him parking on the public street, try getting over it. Any car can park there, including his.
Even if you try to solve the (perceived) problem by limiting hsi number of overnights, I don't think you would, because even if he left each night at midnight, he'd still have taken up the space during the time the neighbors would have come home.
And your neighbors are grown adults and should understand the first come, first serve rule of the parking.