RELENG_4_8 to RELENG_4_9 question

[Bryan Cassidy]

I am currently using FreeBSD 4.8-RELEASE and I did a cvsup
/usr/share/examples/cvsup/standard-supfile to a RELENG_4_8. I haven't
done a build/install world and finished the update of the system. What
I'm wondering is sence I did a cvsup to the latest security patches etc
for 4.8 should I go on and build/install world or can I just do another
cvsup but to RELENG_4_9 and do a build/install world to get update 4.8
to 4.9? 

Thanks