I've got one of the large caravan jobs in mine. Either 500g or 1kg, can't remember off the top of my head. I've got too many rifles to fit in a cabinet so they are in a locked room, and one of the walls in an 'outside wall'.
It's only been in there a week and the indicator hasn't started to change colour yet. Will check again tonight but I'm sure it will be months before I need to worry about it