I just let it sit idle, honestly. I can't seem to find a good investment wherein I would get a guaranteed passive income out of my bitcoins. Too many scam sites and platforms appearing out of nowhere. Cloud mining can't be that profitable, so is trading because I lack the time to execute trades.
Well there is, but yes indeed about 75-80% of the coins should stay idle.
It's too bad since it would be better for the economy if those coins were used, however until we can establish a trusted bitcoin bank (without ponzi scheme), we cannot deposit our coins anywhere safe.
Not even exchanges are safe after Gox and Craptsy.