Many of you have noticed that our API rate limiting is stifling to put it mildly. We heard you and we, yet again, changed the way we limit API use. You'll like this one we're sure...
There's a limit of 450 requests within a 15 minute window. If you go above that you're temporarily blocked. You can make all those requests within anywhere from 1 second to 15 minutes.
TL;DR: Space out your requests so AT LEAST one second passes between each and you can make requests all day. Go even a millisecond faster and you'll hit a brick wall REALLY HARD.
There is no limit of the number of requests. You are limited to how often you can make requests. There are no hard numbers in this, its more of a throttling algorithm that will restrict aggressive apps and reward those that are well behaved. If your app spreads out requests to at most one per second you will not have any problems and can make requests 24/7. If the time between requests is less than 1 second you will be restricted and the more of these requests you make the more likely you will be blocked and proceeding amounts of allowed requests will dramatically drop.