Your old Suica card remains valid as long as it has been used at least once within the last 10 years. The 10-year expiration clock is based on the date of your last transaction (either a ride or a purchase), not the date the card was originally issued. If your card has been dormant for longer than a decade, it is technically expired, and any remaining balance or the ¥500 deposit is forfeited to JR East. However, if you are within that window but the card fails to scan at a ticket gate, it may simply be "locked" due to inactivity. In this case, you can take it to any JR East station attendant who can quickly "re-initialize" it for you. Note that this 10-year rule also applies to other major IC cards like PASMO and ICOCA. If you have a Welcome Suica (the red tourist version), be aware that it has a much shorter lifespan—typically expiring exactly 28 days after purchase regardless of use.