The most important thing the Bible says about this is that no matter how young or old we are, God has a purpose for every stage of our lives. We're never useless if our lives are in God's hands -- and we'll never be bored.
Most people in Bible times worked as long as they could; they had to, because life depended on the success of the next crop. In other words, the modern idea of retirement -- stepping aside while we're still able to work -- would have seemed strange to them. This doesn't mean it's wrong to retire, however; retirement isn't forbidden by the Bible.
One exception was the Levites, who helped in the worship services in the Temple and were allowed to serve a maximum of 25 years. The Bible says, "At the age of fifty, they must retire from their regular service and work no longer" (Numbers 8:25). However, they still could assist in some ways, if they were able.
See your retirement as a gift from God -- and then ask Him how He wants you to spend it. Perhaps He'll give you opportunities to spend more time with your grandchildren -- and if so, ask Him to make you an example of faith and love to them. Or God may have something new for you, through volunteering to help others in your church or community. Take time also to draw closer to God, praying for others and studying God's Word, the Bible. Let these be the best years of your life -- by seeking God's will, and then doing it.