30 Days to back out - there's your limit
If we assume that you're using that service as the sole storage for your data, and you have a download speed that averages 1MB/sec (and there's no throttling). That means you've would only be able to get 2.5TB of data off in time when you close your account (or when it is closed for you, perhaps because Amazon decide the offering is not viable). So a sensible user would assume you actually have a 2.5TB limit (even then only if you have as good an internet connection as a 1MB/sec avg 24/7), as you cannot dependably retrieve any more back from it.
2.5TB is still pretty good for cloud storage mind you.