I think volunteer hours are relevant only if they're something you're passionate about, and I think it speaks more if they're over a long period of time than all at once.
As an example, I've been volunteering with the Red Cross for about four years, and I've got about 500 or so hours logged with them. I didn't even know until this year how many hours I'd volunteered; I assumed it was more like 150 hours. But it turns out that just two blood drives a month over the course of four years is way more than that.
So yes, if something is important to someone and they take it seriously enough to invest regular hours in it (not even that many - four hours per week ends up at 200 hours per year), they very well could wind up with 1000 hours.
On the other hand, 1000 hours in just one year sounds a bit fishy. That's about 20 hours per week; how do they fit in work, classes, and other ECs? Did they do it because they loved it, or was it because they felt it would look good on an application? The adcoms will look at these things and probably make judgments on it.
TL;DR: Lots of hours are possible and good over a long period of time, but short-term (while possible) seems fishy. Look at it critically.