NetBSD like other BSDs have base and packages.
I am not too concerned about base since the risks are rather quite low. Plus I doubt there are any remote holes in base. Local vulnerabilities may exist, but for "desktop" use these are probably a non-issue.
I would be far more worried about packages from pkgsrc. You can see issues from the "daily insecurity output" mail sent out daily. In that reguard, NetBSD gives you better security warnings for packages then other systems (AFAIK). Using that report you could act on them.
Plus, for "desktop", I think the only major concern is Firefox (and other browsers), I noticed just recently Firefox was updated to the new version on 10.1. So at least for Firefox, you are kept up to date. I think the same could be said for Thunderbird, but I am a mutt user so I have no opinion or knowledge about TB.
HTH