syncing -current with -snapshot

[Brian <bwaichu_(_at_)_yahoo_(_dot_)_com>]

The way I install openBSD is from a snapshot.  I work
with the snapshot for a few months before doing a
fresh install with another.  I will sometimes upgrade.

I also pull down ports and src tarballs no later than
a day after I have installed openBSD.

Should I ever cvs up my port tree without doing a cvs
up and re-compile of my kernel and userland?  

For example, with firefox 1.0.1 soon to be available,
can I do a pkg_delete of my old firefox and pkg_add of
the new version without re-doing my kernel and
userland?  Or can I compile sources from the port tree
after I have done an cvs update?

I monitor:

http://www.openbsd.org/faq/current.html

for major changes in -current.  If libraries have
changed, then I just do a fresh install.

Anyway, just looking for advice for how closely I need
to maintain the gap between my snapshot install and
any cvs updates to my port tree (assuming no flag
days).

Thanks,

Brian