The transformers eventually ( 6 months tops from my experience) will burn out, and some with a little singe or smoke as well. The type that have a regular power cord with the power supply being inside the body of the component itself have not done this in my experience. In the USA using the radio as a source makes you subject to the same regualtions as the radio station which you are re-broadcasting as far as the3 FCC is concerned. Using music which is not public domain, or licensed for re-broadcast like MUZAK, puts you in violation of copyright laws in the USA.
Now for the practical side of the equation. If you look on your matress you will see a tag that says do not remove under penalty of law, and being busted for a copyright violation for MOH is about as probable as having the matress tag police come visit your bedroom. It could happen, but I do not know amnyone who has had it happen, yet. My remedy is to explain the legality, sell them whatever components they want, connect everything except the actual plugging in of the 1/8"/RCA stereo plug source , and let them do that.