I found the feeding got suddenly much easier at 12 weeks. That, or else I just stopped thinking about it so much. Either way, it doesn't take any effort anymore unless you include the arduous task of eating my own body weight in chocolate everyday so I can't take any credit for that. S & R do the hard work with the permanent munchings 
The culminative effect of the no-sleep does concern me a little. My executive function is definitely somewhat impaired occasionally not there at all. DH should make me play chess every day to guage whether I am allowed to leave the house in the car, just like Leo and the President in TWW 
Seriously though, sometimes I am yawning so much that my eyes are watering and tears rolling down my face, much to the DCs alarm. Have to explain that am not upset, just ever so tired. They look at me suspiciously as they don't ever get that tired. Ah well. Another couple of months and I dare say this will have passed. And then they will be trying to move around!
Twins are twice the work (more than twice probably) , but I get twice the number of joyful faces and excited wiggles in the morning. Makes it all worth it :)