I think holding a bitcoin for a long time is a good thing cause the value of bitcoin keeps on getting high just think about this when bitcoin made its first appearance the worth of 1Bitcoin is 0.08$ look how much its price grow from its appearanve
This is true but I think apart from or say along with holding you can smartly invest your bitcoins and grow them while you are holding them, just do not sell them for fiat too soon.
Now if you wonder which site you should invest at, then I would suggest investing in gambling sites bankroll.