I have got one banjo (zither-banjo type, not playable) and a bodhran standing on a bookshelf, the instruments I am playing are sitting in their gigbags in a corner of my sofa or within reach. Harmonicas etc. are in their cases on the bookshelf to, with the exception of one on the table...
Is your friend suggesting to hang them on the wall on the chance that the banjo falls down and dameges?????????
Best wishes
Ernest