I have a large sim family who have extensive inventories, produce, fish and loot from adventures and I have had to change households several times and so far, so good. Everything is intact. I have been using the method instructed at the sims3 site that someone recommended to prevent losing everything in inventories. That is, when you start to save, go to Main Menu, save, go back in same game, then Edit Town and change households, and all this tapdancing seems to work.
I have a couple of sim games where sims have partnerships with deeds but do not have to change households as they are the only household in that game that I play.
Supposedly this last update/patch fixed this.