Bitcoin doesn't pay you interests rather it increases the value of your investment, there is no definite ROI in Bitcoin, the value of your investment increases overtime as you continue to hold.  the longer you hold into your investment, the possibility of it's value compounding and over time, even the new compounded value would still compound upon itself to give a bigger value when you hold longer.

This compounding effect is what short-term profit takers tend to miss out upon. Those that sell completely loose out totally to enjoy a bigger value of their investment, those that shave off profits reduces the quantity of their holdings and invariably limits the compounding effect on their investment. The more quantities you've, the bigger the value of your investment on the long-run.