Wait why ? Is it not better for ur btc (when u not using it) to sit on cex and earn u some small profit, then when u need it u can cashout. Then to sit in ur wallet doing nothing?

I agree that profit is nothing over what u need to invest, u can't get 100% return in forever . But when u invest some (that u can afford to lose) and do some trading, when waiting for price change, mining and if u add to that few good refs, u can make some nice profit.