That just means I can't do more than about 15 solves a night until I get much faster. I'm averaging 3 minutes a solve now with a best time of 2:30.I would recommend doing full solves. Reasons? In 4x4 you need to be good at all parts, not only the beginning. After doing doing centers and cross you need as well to be comfortable with edge paring in 3-2-3 scheme. Next goes normal solving but recognition of f2l is different than in 3x3 becasue of double edge - you brain needs to used to it. And the final - parities. Without practice it can be harder to recognize it. That's my opinion. Literally doing full solves let you to be comfortable with 4x4 and Yau method. You can bring your times quite easily to 2 minutes barrier.