I know chests are safe, the items that I put there will stay forever. Is that also true for cupboards? Because I like to separate chests according to the item category.
I'm pretty sure that all containers in your house are supposed to be safe, there should be no difference between cupboards, dressers or chests. I've been keeping my stuff for a long time now in all kinds of containers in my home, nothing has vanished so far.
There is also a loading screen tip saying
Items can be safely stored in any container in your house.
I wasn't fast enough to get a screenshot of this loading screen