The rate is a daily interest rate.
The duration is a maximum duration - the person who borrows the bitcoin can repay it at any time, but must be prepared to repay the loan by the end of the duration, or the exchange will liquidate their altcoins to recover the bitcoin and automatically repay the loan. The profit you will get from each loan will be (daily interest) * (actual duration of the loan).
The effect you are observing is that of people rapidly borrowing and repaying the loans. If a borrower gets a loan at a high percent interest rate, and a short time later a lower interest offer becomes available, they have an incentive to repay the high interest loan and pick up the new loan at a lower interest. There are bots which manage this process automatically for traders, contributing to the rapid borrowing and payback cycle you have observed.
so what happens if 1 person borrows my loan for 3 hours. Do I get the full loan amount or only 3 hours worth of the total daily value? And once he repays back and someone else borrows. Does that mean I get an additional return on top of my requested one? – Patoshi パトシ – 2017-05-05T15:52:20.423
You will receive interest at the daily rate, but only for the actual duration of the loan. If you loan 1 bitcoin out at .1% daily rate, but the borrower repays you after three hours, you will receive (1 .001 3 / 24) in profit, which calculates out to .000125 bitcoin. If they kept the loan for the full two days, you would receive (1 .001 2), or .002 bitcoin in interest. – brandondoge – 2017-05-05T15:55:19.060
ok i see. so locking your loan in for 2 days at a high rate is actually not worth it then? What is a good % loan offer that usually gets filled all the time? – Patoshi パトシ – 2017-05-05T20:21:40.567