With Perptual trading, when you have a position, the longer you let that position opens, the more interests you will have to pay for that exchange. Usually exchanges will have different shifts of funding rates within every 24 hours. It can be 3 or 4 shifts every day.
So even if your position at the end when you close it at profitable exit price, the longer you let that position opens, the less interest you will get at the end because the more in interest you will have to pay for exchange.
Perpetual trading is not future trading.
Funding rate varies based on the difference of price on spot market and futures market. Funding rate will be charge negatively or positively on all open positions base on the current market condition. Funding rate shifts to negative or positive every exchange reset period so its not necessary that your open position will accumulate more interest since it depends on the market trend from time to time during your open position. This is how funding rate works on crypto.
I created this kind of topic on local board before since you can have profits by taking advantage on it.
https://bitcointalk.org/index.php?topic=5399697.msg60195105#msg60195105