The things ecozombie said, plus this....
Sleep for 24 hrs, 31x in a row, then fast travel out of town and back. Everything in the world, which can reset, should reset then, and reduce both lag and load screen time.
About eco's mention of things laying around, I've noticed a definite difference in lag, between having no Hearthfire home, a Hearthfire home without an armory, and a Hearthfire home with an armory. The more stuff that's "out," the more the system has to render. I once tried to fill a room with my loot, just create big piles of it, in the small round room at the back of the house. I took everything out of containers and trudged through the house, to that room, and started dumping it. By the time I got to about shin high, the lag was so bad I could barely move. Picked it all up, and things were fine again.