As much as Frontier likes to refer to the "realism" of the game... it isn't realistic at all. There is no life to this gamel. In this kind of future, why is there no communications when you enter a populated system? Where are the radio stations? Where are the communications from the ports and planets? Seriously, why is there no radio? Did they all become boring in the future? How are we supposed to be excited about trucking fireworks to some station if we cannot see the fireworks when they go off? Why can we not see NPC's unloading our cargo while we sit in the station? Where are all the women? Did it become normal in the future to not have any women pilot ships?
As far as stacking missions... it would be realistic to be able to stack as much as your cargo could hold without having to leave the station, or take a nap, or sleep... that's how I see logging out and logging back in anyway.