If the grease in your bearings has not been contaminated with water, I'd bet a whole bunch of money it's just fine and dandy. Let's face it, there are millions of cars running up and down the highways right now with wheel bearing grease that is not only older than your trailer, but also have a whole lot more miles on them. A LOT more miles.
Your trailer bearings and brakes are fine. Go enjoy camping with it. Something tells me you're not planning on dragging this thing from Key West to Seattle and back at 90 mph here next month.