1.7 my game ran at solid 29-30 FPS, 1.8 and ALL DLC 20-30 FPS, 1.9 22-30 FPS. After 1.8, I started a new game and lag on my way to river wood, quit olaying the game for a while. After reinstalled everyhting and rebuilt the database and have 30 FPS SOLID with the same file. Oghma'd him at 6 MB and at 8 MB lag kicked in, I had completed eveyrhting with only one quest in my log and lag is there but not as noticeable.

1.9 came out, new character, lag on the way to riverwood, stopped playing but haven't continued yet, I'll try him again next time I have the chance and report my experience. So the tip is start a new game, if it lags, save wait a couple of weeks, reinstall everything, and rebuild, lag should be solved. Tell me if it work for you guys.