Males have been collecting 'things' for thousands of years. It started with sticks to make spears out of, rocks to make axes, oddly shaped bit of wood to make other things. Eventually as manufactured items became available, this instinctive trend continued - and ended up with you - and others - collecting things like bass guitars. As long as it's not negatively affecting anyone else - or yourself - I wouldn't worry about it...
So, basically, as long as he throws them at someone or something he'll be alright?