If you're prepaying your mortgage, you should stop right away. Interest rates are rising: current 30-year mortgage rates are 4.5% or higher, up almost a full point from the lows a few years ago. If you were lucky enough to refinance your mortgage near this low point, hang on to the cheap money as long as you can. It may be many years before you can refinance into another loan that's cheaper.
The flip side of higher mortgage rates is higher rates on savings accounts. Online banks offer daily rates around 1.40%, and 12-month CDs around 2%. An extra $500 paid to your mortgage each month is inaccessible until your mortgage is paid off in full. But $500 in a savings account each month – with interest – can add up to real money. Online savings banks are a great place for money you may need soon, like your rainy day fund or your vacation savings.