I made mine to be portable, and to be safe to use whether the kit is double insulated or not (most is anyway).
The reason I have fitted a double pole RCBO on the secondary is that it is possible that a fault could occur on one secondary leg, but the other could still be live, for instance making the chassis of a bit of(non double insulated) kit live. I appreciate this is pretty unlikely, but I prefer to err on the side of safety, having worked in the high voltage industry for coming on 30 years now, and been to seven funereals of work collegues, some killed by some unlikely circumstances, I prefer the belt and braces approach. That's my choice, I couldn't care less what approach others wish to take. In any case, they are easy to fit, and I doubt I could hear a difference in SQ with and without, so why not fit them anyway, also you don't know what kit you may buy in the future.
Mine has been on pretty much 24/7 for coming on two years now without any issues.
“Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”
Hunter S Thompson