If you have already added your credit card to paypal, then one day it is most likely to expire. All credit cards do have expiry date (once in every 3 yrs), which after that your credit card company will automatically renew and send you the new card (with new secure code/CCV and expiry date). This may vary from country to country and the card issuer as well.
Just keep an eye on the expiry date, because if you dont update your credit card expiry date with paypal, the card will automatically get deactivated / removed and, if that happens, all your active subscriptions linked to the card will get automatically cancelled, which might cause you more inconvenience. Of course! Paypal will notify you by email if the card is removed because of the expired date.
To update your credit card and new date, just login to your paypal account
Account > Profile > Credit/Debit Cards > Select Card > Enter new expiry date and Verification code > Save
If you use your credit card, paying for other services or hosting using subscription (not with paypal), then you will need to update your expiry date and verification number there as well. If not, the card transactions will get declined, once the expiry date has passed.
For example, if your card is expiring on 01/2010, then any transactions after Jan 2010 will get declined. Fortunately, most credit card companies will replace your old card to new one, before one month or so
