You know what I find a bit of a mixed bag? Time limits on contracts...
When someone gives me 36 minutes to deliver urgent data, I can do that. I drop everything and I rush over, maybe picking up some trade goods if I know a good trade. I know that this contract is urgent, I know I cannot do anything else at the same time. I know where I stand and I know I can do it quickly.
When I have a week to kill 15 pirates in a nearby system, I'll take that mission even if I just sit on it. It's something to do when I am in the area. I know I have time and even a day away from the PC is not going to be a major issue. These long-term ones all seem to be combat, so it's fairly easy to park myself at a waypoint or hunt Unidentified Signal Sources. I know I don't need to worry.
The trouble is when they ask for 6 dead smugglers and give you 12 hours. I am not sure about other players, but that's awkward unless I know I will be around for a while. It's not long enough to leave unfinished overnight, but they tend to ask just enough of you that you need to set aside an hour or more just in case the random number generator is not playing nicely. This is worst when you need to gather X number of illicit items from Weak Signal Sources, because you just know you'll end up endlessly fighting pirates or smugglers instead. Also, you will need just one more item than you find in the first debris field, so you stay paranoid that the next jump or interdiction attempt will be some form of system security.