After a year or two of collecting miles and points, you might be tempted to begin "churning" credit cards -- closing and re-opening accounts to receive a second, third or fourth sign-up bonus after meeting the minimum-spend requirements. Some banks won't let you earn a new bonus within a few years of closing an identical account, while others are much more willing to hand over thousands of points in exchange for another shot at keeping you as a customer. Either way, you'll generally need to close your account before opening a new one.
We won't get into the intricacies of churning, but this activity definitely comes along with some risks. The primary negative to consider is that closing your account (even if you plan on re-opening it a short time later) can cause you to lose your hard-earned points, depending on the type of rewards currency you've managed to rack up.
Generally, accounts that push miles to a frequent flyer program managed by an airline or a points account with a hotel chain (and not the bank) are entirely isolated from your credit card accounts. So if you close a card, your miles with the airline will remain in that account indefinitely. Some cards prolong your mileage expiration date for as long as you maintain an active credit card account, so that's something to consider, but generally, the bank can't touch the miles in your frequent flyer account, so those are yours to keep even after you close the affiliated card.
Points held directly with the bank are an entirely different story, however. Accounts with American Express Membership Rewards, Chase's Ultimate Rewards and Citi's ThankYou remain the property of the affiliated credit card program. When you close a line of credit that's linked to one of those rewards accounts, your points will disappear, assuming that's the only credit card you have associated with that same rewards account.
One way to safeguard those points is to open a new account that's set to deposit points in your existing account. If you have an American Express Gold card and an EveryDay card assigned to one Membership Rewards account, for example, you can close one of the cards without the risk of losing your points. If you shutter both lines of credit at the same time, however, or if you only have one card linked to that particular Membership Rewards account, you will forfeit your remaining points.
The best thing to do is to have the bank representative clarify whether or not you'll be able to keep your points after you close the affiliated card. Policies change from time to time and the customer service representative will have access to the latest information. They may be able to move points from one account to another, or make recommendations regarding how to secure your balance.
If it's clear that you'll lose your points but you still need to close the card, transfer your points to a partner program, such as an airline or hotel chain. Generally, it's best to keep your points with the credit card program in order to maximize flexibility, but if you're about to lose them, you should be able to retain some of their value by moving them to a partner. You'll need to keep the rewards card open until the transfer is complete, however, so don't have your bank close your card until the points show up in the partner account.