By general rule I look at it like this. A guy should never be wearing a jersey of someone of similar age or less. If you're 35 and want to break out that #55 jersey then go ahead, if you're 35 and wearing one that says Cooper on the back then :naught:. Same goes for NFL.
I have a old #10 jersey from when I was 8 or 9 years old because Walter Lewis was my favorite player. I do not still wear it though