It doesn't show anything on my desktop about any time limit.
SP3 contains all Hotifxes for XP (includes IE6/IE7 updates, but does not contain IE7)
Networking:
"Black Hole" Router Detection
Network Access Point (NAP)
Functionality:
Descriptive Security Options User Inface
Enhanced Security for Administrator and Service policy entries
Microsoft Kernel Mode Cryptographic Module
Setup:
Windows Product Activation (Affects other Windows programs activation, this is not WGA)
It only contains a few new features, which I doubt most users will use. It should be a small update on Windows Update when it is released, since most people won't need all the updates.