I should use interest and profit differently to avoid confusion.
Well, I am not a fun of it and not so familiar with it.
But as for trading derivatives (perpetual swaps and futures). There's funding rate that keeps changing from positive to negative every 8 hours according to most derivative exchanges and the market conditions dictate it, not how long someone keeps their position open.
Also, the exchange does not benefit from the funding rate, as the traders pay themselves depending on what side of the funding rate they are. The exchange only benefits from trading fees, theoretically.
That is seem very risky.
Very different if we compare with spot trading,
we only get unrealized loss if don't sell the coin and the coin still there.