How long can coffee beans preserve its flavor?

After roasting they will keep for about 6–9 months if they are sealed.
It is best to store them in an airtight container. I own a vacuum sealed coffee bean container on my counter. It’s overkill for me because I go through it in less than a month.

I do the same as @Forever_Free, I buy from the roaster (Graffeo Roasting Company in San Francisco) and they stay in great shape for a week, second week they lose a bit of their freshness, but are still good for a pot of coffee (I go through a pound every 10 days).

If you do not use the beans quickly, you can keep them in an air tight constainer in the freezer and they will last a very long time, like a year. When we had a vacation house, we woud keep beans in the freezer for months.