From what I've observed, it seems like nearly all planes land and depart within about a three hour window in the afternoon. I'm not so sure a 3 hour process to check-in is so much a requirement, as it is the problem of a huge mass of travelers arriving and departing within a short period of time. If you are able to use the priority check-in lanes and use the baggage handlers, that is helpful. My wife and I arrived at STT about 11:30 am, about the same time the Delta counter was opening. The terminal was practically empty at the time, and I thought perhaps because it was a Thursday. We checked our luggage, cleared Customs, Immigration, and TSA within 15 minutes. At about 2:00 pm the entire waiting lounge was completely packed, not an empty seat anywhere. I hate to waste 2-3 hours waiting in the lounge, although this is one option to avoid the very large crowds attempting to check-in, clear Customs & Immigration, and pass TSA all at the same time.