Performance inconsistency

What's the deal with NVil performance when viewing subdivided models? Sometimes I open the scene and subdivide my objects twice and I get 5 fps with 640k polys visible in the viewport and then after working with the scene for some time and adding even more polys into the scene I get 60 fps with even greater polycount.
Then I restart my program, load up the scene again and 60 fps are kept, but when restart it and reload the scene one more time I get slide show again?

Okay, I'm going to answer my own question.

One word:

"BACKFACE IN GRAY"

If you guys want to increase subdivision of your model, you really want to keep this thing off. It turns out to be a REAL resource hog. Can't its performance be improved?