"updating" from what to what? If you are wondering about Xenocara,
I hope you are intending to end up on -current. Otherwise, mostly
just a curiosity question to me, as the answer is always the same:
No, you don't need to build it at all, you use snapshots, or release,
depending on the "to what" part. If you have to ask questions about
building, the answer is "don't". If you don't have to ask questions
about building, then you already know the answer is usually, "don't"
yes, you keep them in sync with the rest of your system.
Same as always...
Nick.