It doesn't matter if the mission takes 1.5mins or 5mins to complete. You still have to wait about 10mins in total for loading into the game and loading back into free roam.
10 minutes in loading times? I'd never do this, if that were the case. What kinda third world interweb you usin' bwa?
It's literally less than a minute between hosting job from the pause menu to get into the game for me.
Maybe I'm exaggerating. I'll time it tonight. It's definitely not less than a minute though with the time taken for people to "join" the game. I would guesstimate that there's about 30 secs for the mission to load for me, 2 minutes for friends to be added and join, 45 seconds for the game to load up once I hit start, then at the end, there's a review screen that can take up to 90 seconds for everyone to vote whether they like/dislike the job and click continue, then there's the voting screen. If you back out of that, you may have to wait 2 minutes to get back to free roam.
So that's about 7 minutes in total.