It is always better to take apart and inspect, but it means nothing if you do not know what to look for.
Just what percentage of the TT owners even know what a drum brake is let alone how to check one out. The same with bearings and hand packing.
The trailer axle industry knows this and has addressed the issue with fairly simple solution.
It is true that much of the TT maintenance information appears on YouTube and other sources for those who like doing things themselves.
However, I will admit hand packing bearing and cleaning up brake shoes looses some of it charm when you are sitting on the ground covered with grease and brake dust and grime.
I suspect that most folks will leave it to the dealership though my experience with them was not been very satisfying.