There is no automatic blocking based on the frequency of access. And you would get a “403 Forbidden” error if your IP is blocked. But this blocking is done manually and only for IPs with more than 10 requests per minute.
The data file contains the data of the last 5 minutes. Most sensors will send new data every 2 1/2 minutes. So it should be okay to request new data every 2-3 minutes.
The problem: Most computers are time synced. And so most requests are done at the start of each minute. This may cause time outs or empty results for some requests.