OK, so I did a little experiment last night and slept with them on. They stayed on with no problem because I have the airlock device.
I found that it was too painful to pump to the extent I normally do and lie down. So, in order to not be in pain and get some sleep, I had to not pump as much. Infact, in the middle of the night, it got so painful that I had to let some air out. As a result, eventhough I slept all night with them on, I still only got as much swolleness as I did when I wore them for 2 hours, but really pumped them up. So, in my opinion, it's not worth it not getting a good night's sleep because you can't pump them too much. And I had red marks under my boobs where the cups dug into my ribcage too much. So, for now, until Lucy can come up with something that would make it more comfortable to wear for an extended period of time, I will not be sleeping with them on. But it's been 12 hours since i took them off and I'm still quite a big fuller. There's definately progress being made.