I'm going to be really boring and say that it's all subjective.
What's strange though is that I'm really horrible in judging how long people have been around for. Some members like hylianshroom, musical_zombie. and Holic seem to have been around for aggeeees, but they only really joined in the past few months. On the other hand, I've been more active in the past few weeks than I ever have (don't worry, I'll bugger off when Uni kicks up again

) and I'm only just noticing people who've been here for years. So I suppose that from my perspective, then these people are newbies, even though they've been here for waay longer than I have. XD
As for being a vet, that's a pretty hard question to answer. Personally, I think that a year is a pretty long time to be on a forum and I think that if you've made a sizable impact in 12 months, then I'd consider you to be a vet.
That definitley includes Sarah and Double Dee One Two Three.
Float your newbies.