Yeah, you would start your new job at May 1st if you sent in your resignation during January. It's a bit long I feel, when I first resigned last year (in January, even), I mentally started to check out towards the end. A month or two is fine to wrap things up. But 3 months + what's left of the current month was a bit much. But as I said, it goes both ways, and it's almost impossible to get fired here, so it's worth it for the peace of mind knowing you'll always get paid next week, month etc.
Where I worked before the avg employee had worked there for about 3-4 years, and that number was heavily influenced by the new hires not having had the opportunity to work that long yet, even. I feel that's true for many of my friends as well, those having switched a few jobs since graduating have stayed avg ~3 years.
