It varies from team to team depending on a variety of things, including the team's weight/power output, riding terrain, e.g., climbing 500 hilly miles are a lot tougher on a chain than 500 flat miles, and of course attention to maintenance/lubrication.
Your best bet for getting the most life from your chains without putting unnecessary wear and tear on your cassette cogs and chain rings is to routinely check your chain for wear. You can use a 12" ruler or you can buy a "chain checker" tool from Park Tools to do the checks. The more you ride the better idea you'll have about how often you'll need to replace your drive and timing chain.
You can read more about chain maintenance here: