We're not diligent about locking the trailer up if we're just going with the kids down to the playground, or up to the store or something. We're usually in close enough ear shot that the dogs will let us know if anybody's around.
But I absolutely make sure everything's on lock down if we ever leave the park.
To the OP, our home safe only contains the items I don't want to burn, like the kids birth certificates or our marriage certificate. Even accounting for going full time, I can't think of what you'd need a safe that big for.
But hey, at only 140lbs, it's not like it's necessarily bulky. If fits nicely under the love seat and as you said it's an out of sight, out of mind thing. Nice install.