Perhaps it's a deliberate gameplay decision though - force the player to go out and do other things in the meantime.
I expect those missions that take time will be relatively rare, maybe even confined to just the main quest arc.
(Granted, it seems like a perfect vehicle to introduce microtransactions or something, and that... wouldn't be so good, especially if it was in SP.)
That doesn't always work. Sure, it 'encourages' players to go out and explore in the meantime, but there are many types of players. What if a player explored already? What if they play fast and still have time to spare after doing a good amount of exploring? What if they just want to focus on the missions instead of exploring? What if they have a limited playtime and want to spend their limited free time doing different things in-game?
'Forcing' is rarely a good thing when it comes to games. Sure, you might have fun, but you might also end up just killing time and get bored if you are forced to do something in-game you didn't feel like doing yourself.
I'd just like to know what to expect for when the game comes out.