I have spent more time refreshing than I would admit in polite company. 5 mins is literally nothing. Before I made real FPs last year, I spent hours poking and prodding the system to figure out any way of improving my results. Different crowd levels, different times of day, different party size, different browsers. Some things help. Believe it or not, a browser over the app have a noticeable difference in success rate (for me). It's a technical puzzle and I'm an engineer with a vested interest.
I really do believe it comes down to how Disney is dividing up the bandwidth between servers. I have zero proof of that but that's my suspicion. Based on who reports having an easy time I think it's people with APs (or a subset of people with APs) who are directed regularly to a server that doesn't get as much traffic. Possibly completely unintentionally by Disney, who knows. But that's totally unscientific with nothing but scant anecdotal evidence. But it helps me when I get frustrated that I'm not in the other half.