We decided that we wanted to do high level runners, so I started out giving karma out like candy, some sessions the PCs would get 20 from a completed mission. Now that we are at the level we want to be (really experienced, decently powerful, able to take on the elite corp wageslaves if they have to) I has slowed the karma down to the normal rate where I will give 2 karma each week(or ~6ish hour session if we go over that they get bonus), then 1-2 for completing objectives, highest dicepool /4 and so they average 7-10 by the time they complete a run.