That's solid progress. Think about it this way... if you could sustain that progress, how big would you be after another six cycles? If you are doing eight week cycles, then that's about a year from now. You would have gained another 1 1/2 inches to your arms, 2 1/4 inches to your chest and 1 1/2 inches to your quads. Maybe that doesn't sound like a lot when you just type it out, but that is significant progress over the course of a year.
In reality, you probably won't be able to keep going like that especially if you are going to be cutting at some point, but it is a good goal to shoot for.