Only if the value of the assets goes down signficantly. Your loan based on Enron stock needs to be paid back (or recollaterialized), but one based on a stock that's been doing well or on a reasonably diversified portfolio can probably avoid repayment until you sell or die. From what I've seen, asset backed loans will have a % limit of value for initiating a loan and a higher % limit to keep the loan, but both limits are often much lower than a brokerage margin loan.