My game starts freezing around the 400 hour mark, locations won't load game just freezes up. Bethesda must know about this. Is there any new patches coming out or what can I do other than starting a new game.

1.6, the recent patch, fixed this for me.

I'm over 400 hours (420 plus or something.)

I got system locks upon entering dark brother hood sanc, various palaces, most forts, some crypts, a lot of outdoor locations (since near ninroots),
my house in markarth (inconvenient, had all my stuff and wife), as well as when leaving the companions hall.

This patch fixed all that for me, dropping my savegame minimum size from 20 meg to 17 meg too.