If you are close to a major purchase where you know you will need a loan (house, car), then keep them open. If you think it will be years before you need a loan, then close them and be done with them. Your credit score will have plenty of time to recover.
I don't think credit scores are as fragile as some people here think. If you have had a poor credit history, perhaps you need to worry, but if you have a solid credit history, your credit score is going to be fine. Most of us can qualify for way more credit than we can afford.