API Call Rate Limit on unlimited plan

When was the rate limit on API calls implemented on the unlimited plan? I’m assuming last night/this morning since I didn’t run into a rate limit issue until this morning. Is there ANY WHERE that I can see what changes are going to be made and when?

Each morning I use the API to pull a list of ETB symbols. That’s usually 5000 - 6000 symbols. From that list of symbols I run a multi-threaded process that pulls bar data to screen the symbols for the ones I am interested in. Up until this morning, that process took about 30 seconds to complete. With the 1000/min rate limit on the Unlimited plan, that process will now take 5 - 6 minutes. Is there a quicker/better way to accomplish this without exceeding the 1000/min rate limit?