Yes, the interest rates on money market and savings accounts can change at any time, and without notice. Currently, rates are at record levels due to the Fed's current rate-hike campaign. But that could soon come to an end, and when the Fed begins lowering rates, money market and savings account rates will also decline. If you instead want to lock in a fixed interest rate on money you won't need for a while, one of the top-paying certificates of deposit (CDs) is a great option right now.