As Billy said: you will only have to upgrade when Sun release an exam for a new version of Java.
From the Sun FAQ:
What is Sun's new Certification Policy?
Beginning with all Sun certification exams taken on or after August 1, 2003, certification offerings from Sun no longer have an expiration date. Rather, certification offerings are based on a version of technology. The certification date and exam version will appear on both a certificate and an identification card with the applicable certification title.
Recertification is no longer required to maintain one's status as a certified professional. Sun certification is now directly associated with a version of technology. Nevertheless, Sun highly recommends that you remain certified at the most current technology version.
If a Sun certified professional has already received a certificate and ID card with the printed expiration date, can that professional request another certificate and ID card without an expiration date?
Yes. The certified professional will need to send an email to the firstname.lastname@example.org alias to request a new certificate and ID card. Include your name and Prometric Candidate ID number.
How long is my Sun certification title now valid?
As of August 1, 2003, all Sun certifications are now based on versions. There is no expiration date to your certification title. You may, however, be certified on a technology that is outdated if Sun releases a new exam associated with a new technology version. Keeping your certification current is highly recommended.
[ August 16, 2003: Message edited by: Andrew Monkhouse ]