Borrowers will pay back the borrowed principal amount of ETH plus APR fees accrued over the lifetime of the loan.
Partial Pay Back
ETH provided to pay back the loan will be applied to accumulated fees before being applied to the principal balance. The minimum amount that can be partially paid back is the total amount of interest rate fees that have been accumulated by the loan to date.
For example, if a loan of 10 ETH has accumulated 0.01 ETH in fees, then the minimum amount that can be paid back is 0.01 ETH, and any amount over 0.01 ETH will be applied to the loans 10 ETH principal balance. This will effectively decrease the loan's LTV, reducing probability of defaulting and affording the ability to borrow additional ETH on this loan at a later time as needed.
Depositing Additional Collateral
Additional collateral can be deposited to reduce the loan's LTV ratio and allow for additional ETH to be borrowed.
There is no set time frame that a loan must be paid back in. As long as a loan's LTV ratio remains under the default threshold, the loan will remain open, but will continue to accumulate APR fees over time.