Fermentation stopped too early??

I posted this in the recipe section but haven't received any feedback. On Saturday evening I drained my oatmeal stout into a 6.5 gallon carboy around 9p.m. at about half full I stopped and gave the carboy a good skaking for aeration. I finished filling it and then pitched my yeast starter on top then gave it another good shake to get it nice and mixed up. By 10a.m. the next morning I had a good fermentation going with steady bubbles coming from the airlock. As of yesterday the activity has slowed significantly and I never really got as high a level of krausen as I have seen in some of the pictures on here.

Should I give the carboy another good shaking to suspend the yeast some more as well as aerate or just let it sit? My efficiency was about 75% this time around which is a great improvement on my first batch that was about 55%. The OG was 1.045 and pre-boil was about 1.035 boiling from 7 gallons to around 5.5. Does anybody have any suggestions or is this typical of an oatmeal stout?

Have you taken any more SG readings? That's really the only way to know if it is done or stalled. Airlock activity is a poor gauge for fermentation status. I would avoid shaking at this point - if you do need to resuspend the yeast, a gentle swirling would be safer.

Thanks...I'll take a reading this evening when I get home and see where it is. Is it fair to say that a 75% drop in gravity is a good indicator that it's near done

You're looking at yeast attenuation %s....as far as what is expected, that would depend on the strain of yeast pitched and fermentation conditions. For many yeasts, 75% attenuation would be pretty good. A consistent reading over a few days is the best indication that fermentation has completed.

Well OG was 1.045 and currently I'm sitting at 1.020 so I'm looking at about 55% attenuation right now. Hopefully it will improve over the next couple of days and I'll get closer to 65%...time will tell.